Ancient Economists: Two Views

John Cochrane, reporting from the NBER Summer Institute:

The use of ancient quotations came up several times. I  complained a bit about Eggertsson and Mehrotra's long efforts to tie their work to quotes from verbal speculations of Keynes, Alvin Hansen, Paul Krugman and Larry Summers. Their rhetorical device is, "aha, these equations finally explain what some sage of 80 years ago or Important Person today really meant."  Ivan Werning really complained about this in Paul Beaudry's presentation. What does this complex piece of well worked out "21st century economics" have to do with long ago muddy debates between Keynes and Hayek? It stands on its own, or it doesn't. (In his view, it did, so why belittle it?) 

Physics does not write papers about "the Newton-Aristotle debate." Our papers should stand on their own too. They are right or wrong if they are logically coherent and describe the data, not if they fulfill the vague speculations of some sage, dead or alive. It's especially unhelpful to try to make this connection, I think, because the models differ quite sharply from the speculations of the sage. Alvin Hansen certainly did not think that a Taylor interest rate rule with a phi parameter greater than one was a central culprit in "secular stagnation." I haven't checked against the speech, but I doubt he thought that inflation would completely cure the problem in the first place. 

Sure, history of thought is important; tying ideas to their historical predecessors is important; recognizing the centuries of thinking on money and business cycles is important. But let's stand up for our own generation; we do not exist simply to finally put equations in the mouths of ancient economists. 

But, tying it all up, perhaps I'm just being an old fogey. Adam Smith wrote mostly words. Marx like Keynes wrote big complicated books that people spent a century writing about "this is what they really meant." Maybe models are at best quantitative parables. Maybe economics is destined to return to this kind of literary philosophy, not quantified science.

(via Suresh, who was also there.)

For the case in favor of ancient economists, here is Axel Leijonhufvud:

According to Sir Peter Medawar

A scientist's present thoughts and actions are of necessity shaped by what others have done and thought before him: they are the wave-front of a continuous secular process in which The Past does not have a dignified independent existence of its own. Scientific understanding is the integral of a curve of learning; science therefore in some sense comprehends its history within itself.

... Not every field of learning can claim to "comprehend its history within itself." For the current state of the art to be the "integral of past learning" in Medawar's sense, the collective learning process must be one that remembers everything of value and forgets only the errors and the false leads. But this requires the recognized capability to decide what is correct or true and what is in error or false. These decisions, moreover, must compel general assent. Once an answer is arrived at, it must be generally agreed to be the answer. The field must be one in which answers kill questions so definitively that the sense of alternative possibilities disappears. ... 

A science, or a subfield within it, may come to approximate these conditions because of its positive successes. But two other mechanisms that are not so nice will also be at work. First, the people in the field agree that certain questions, which they would have a hard time deciding, are somebody else's responsibility. So economics among the social sciences, like physics among the natural sciences, had first pick of problems and left the really hard ones, on which their methods did not give them a firm grip, for the younger sister disciplines to deal with as best they might. Second, the insiders to the field will agree to exclude some people who refuse to assent to the manner in which certain important questions have been settled. Both the exclusion of undecidable questions from the field of inquiry and the exclusion of undecided people from the professional group help to achieve collective concentration and intensive interaction within the group. … 

These reflections … offer some suggestions about when scientists might find the history of their field relevant and useful to current inquiry. One suggestion is to look for situations when a research program has bogged down, when anomalies have cropped up that cannot be reduced to or converted into ordinary puzzles within the paradigm. Another is to look for cases in which three conditions seem to be met:
a) certain central questions cannot be decided in a way that commands assent,
b) the (for the time being) undecidable questions cannot very well be left for somebody else to worry about, and
c) the people who withhold their assent from some popular suggested answer cannot be ignored or excommunicated.

... Economists are wont to reduce everything to choices. Economics itself develops through the choices that economists make. To use the past for present purposes, we should see the history of the field as sequences of decisions, of choices, leading up to the present. Imagine a huge decision tree, with its roots back in the time of Aristotle, and with the present generation of economists -- not all of them birds of a feather! -- twittering away at each other from the topmost twigs and branches. 

The branching occurs at points where economists have parted company, where problematic decisions had to be made but could not be made so as to command universal assent. The two branches need not be of equal strength at all; in many cases, universal agreement is eventually reached ex post so that one branch eventually dies and falls away. The oldest part of the tree is, perhaps, just the naked trunk; but the sap still runs in some surprising places. 

If you want to translate Medawar's image of science into my decision tree metaphor, you will have to imagine his sciences as fir trees -- with physics, surely, as the redwood – majestic things with tall, straight trunks and with live branches only at the very top. Economics, in contrast, would come out as a rather tangled, ill-pruned shrub … 

As long as "normal" progress continues to be made in these established directions, there is no need to reexamine the past … Things begin to look different if and when the workable vein runs out or, to change the metaphor, when the road that took you to the "frontier of the field" ends in a swamp or in a blind alley. A lot of them do. Our fads run out and we do get stuck occasionally. Reactions to finding yourself in a cul-de-sac differ. Tenured professors might often be content to accommodate themselves to it, spend their time tidying up the place, putting in a few modern conveniences, and generally improving the neighborhood. Braver souls will want out and see a tremendous leap of the creative imagination as the only way out -- a prescription, however, that will leave ordinary mortals just climbing the walls. Another way to go is to backtrack. Back there, in the past, there were forks in the road and it is possible, even plausible, that some roads were more passable than the one that looked most promising at the time. At this point, a mental map of the road network behind the frontier becomes essential.

Varieties of Keynesianism

Here’s something interesting from Axel Leijonhufvud. It’s a response to Luigi Pasinetti’s book on Keynes, but really it’s an assessment of the Keynesian revolution in general.

There really was a revolution, according to Pasinetti, and it can be dated precisely, to 1932. Leijonhufvud:

By the Spring of that year, Keynes had concluded that the Treatise could not be salvaged by a revised edition. He still gave his “Pure Theory of Money” lecture series which was largely based on it but members of his ‘Circus’ attended and gave him trouble. The summer of that year appears to have been a critical period. In the Fall, Keynes announced a new series of lectures with the title “The Monetary Theory of Production”. The new title signaled a break with his previous work and a break with tradition. From this point onward, Keynes felt himself to be doing work that was revolutionary in nature. 

What was revolutionary about these lectures was that they weren’t about extending or modifying the established framework of economics, but about adopting a new starting point. A paradigm in economics can be thought of as defined by the minimal model — the model that (in Pasinetti’s words) “contains those analytical features, and only those features, which the theory cannot do without.” Or as I’ve suggested here, the minimal model is the benchmark of simplicity in terms of which Occam’s razor is applied.

For the orthodox economics of Keynes’s day (and ours), the minimal model was one of “real exchange” in which a given endowment of goods and a given set of preferences yielded a vector of relative prices. Money, production, time, etc. can then be introduced as extensions of this minimal model. In Keynes’ “monetary production” model, on the other hand, the “analytical features which the theory cannot do without” are a set of income flows generated in production, and a set of expenditure flows out of income. The minimal model does not include any prices or quantities. Nor does it necessarily include exchange — it’s natural to think of the income flows as consisting of profits and wages and the expenditure flows as consumption and investment, but they can just as naturally include taxes, interest payments, asset sales, and so on.

I don’t want to suggest that the monetary production paradigm has ever been as well-defined as the real exchange paradigm. One of Leijonhufvud’s main points is that there has never been a consensus on the content of the Keynesian revolution. There are many smart people who will tell you what “Keynes really meant.” With due respect (and I mean it) I’m not convinced by any of them. I don’t think anyone knows what Keynes really meant —including Keynes himself. The truth is, the Hicks-Patinkin-Samuelson version of Keynes is no bastard; its legitimate paternity is amply documented in the General Theory. Pasinetti quotes Joan Robinson: “There were moments when we had some trouble in getting Maynard to see what the point of his revolution really was.” Which doesn’t, of course, means that Hicks-Patinkin-Samuelson is the only legitimate Keynes — here even more than  in most questions of theory, we have to tolerate ambiguity and cultivate the ability to hold more than one reading in mind at once.

One basic ambiguity is in that term, “monetary production.” Which of those words is the important one?

For Pasinetti, the critical divide is between Keynes’ theory of production and the orthodox theory of exchange. Pasinetti’s production-based Keynesianism

starts from the technological imperatives stemming from the division and specialization of labor. In this context, exchange is derivative, stemming from specialization in production. How it is institutionalized and organized is a matter that the minimal production paradigm leaves open (whereas the exchange paradigm necessarily starts by assuming at least private property and often also organized markets). Prices in the production paradigm are indices of technologically determined resource costs and, as such, leave open the question whether the system does or does not have a tendency towards the full utilization of scarce resources and, in particular, of labor. …

The exchange paradigm relies on individual self-interest, on consumer’s sovereignty, and on markets and private property as the principal institutions needed to bring about a socially desirable and harmonious outcome. In putting the division of labor and specialization at center stage, the pure production model, in contrast, highlights the “necessarily cooperative aspects of any organized society…

To an unsympathetic audience, I admit, this could come across as a bunch of commencement-speech pieties. For a rigorous statement of the pure production paradigm we need to turn to Sraffa. In Production of Commodities by Means of Commodities he starts from the pure engineering facts — the input-output matrices governing production at current levels using current technology. There’s nothing about prices, demand, distribution. His system “does not explain anything about the allocation of resources. Instead, the focus is altogether on finding a logical basis for objective measurement. It is a system for coherent, internally coherent macroeconomic accounting.”

In other words: We cannot reduce the heterogeneous material of productive activity to a single objective quantity of need-satisfaction. There is no such thing. Mengers, Jevons, Walras and their successors set off after the will-o-the-wisp of utility and, to coin a phrase, vanished into a swamp, never to be heard from by positive social science again.

The question then is, how can we consistently describe economic activity using only objective, observable data? (This was also the classical question.) Sraffa answers in terms of a “snapshot” of production at a given moment. Or as Sen puts it, in a perceptive essay, he is showing how one can do economics without the use of counterfactuals.

For Pasinetti, Keynes’ revolution and Sraffa’s anti-subjectivist revival of classical economics — his effort to ground economics in engineering data — were part of the same project, of throwing out subjectivism in favor of engineering. Leijonhufvud is not convinced. “Keynes was above all a monetary economist," he notes, "and there are good reasons to believe” that it was monetary and not production that was the key term in the “theory of monetary production.” Keynes made no use of the theory of imperfect competition, despite its development by members of his inner circle (Richard Kahn and Joan Robinson). Or consider his famous reversal on wages — in the General Theory, he assumed they were equal to the marginal product of labor, which declined with the level of output. But after this claim was challenged Dunlop, Tarshis and others, he admitted there was no real evidence for it and good reason to think it was not true. [1] The fact that JMK didn’t think anything important in his theory hinged on how wages were set, at least suggests that production side of economy was not central to his project.

The important point for us is that there is one strand of Cambridge that rejects orthodoxy on the grounds that it misrepresents a system of production based on objective relationships between inputs and outputs, as a system of exchange based on subjective preferences. But this is not the only vantage point from which one can criticize the Walrasian system and it’s not clear it’s the one occupied by Keynes or by Keynesianism — whatever that may be.

The alternative standpoint is still monetary production, but with the stress on the first word rather than the second. Leijonhufvud doesn’t talk much about this here, since this is an essay about Pasinetti. But it’s evidently something along the lines of Mehrling’s “money view” or “finance view.” [2] It seems to me this view has three overlapping elements: 1. The atomic units of the economy are money flows (and commitments to future money flows), as opposed to prices and quantities. 2. Quantities are quantities of money; productive activity is not measurable except insofar as it involves money payments. 3. The active agents of the economy are seeking to maximize money income or wealth, not to end up with some preferred consumption basket. Beside Mehrling, I would include Minsky, Paul Davidson and Wynne Godley here, among others.

I’m not going to try to summarize this work here. Let me just say how I’m coming at this.

As I wrote in comments to an earlier post, what I want is to think more systematically about the relationship between the network of financial assets and liabilities recorded on balance sheets, on the one hand, and the concrete social activities of production and consumption, on the other. What we have now, it seems to me, is either a “real” view that collapses these two domains into one, with changes in ownership and debt commitments treated as if they were decisions about production and consumption; or else a “finance” view that treats balance-sheet transactions as a closed system. I think the finance view is more correct, in the sense that at least it sees half of the problem clearly. The "real" view is a hopeless muddle because it tries to treat the concrete social activity of production and consumption as if it were a set of fungible quantities like money, and to treat money commitments as if they were decisions about production and consumption. The strength of the finance view is that it recognizes the system of contingent money payments recorded on balance sheets as a distinct social activity, and not simply a reflection of the allocation of goods and services. To be clear: The purpose of recognizing finance as a distinct thing isn’t to study it in isolation, but rather to explore the specific ways in which it interacts with other kinds of social activity. This is the agenda that Fisher dynamics, disgorge the cash, functional finance and the other projects I’m working on are intended to contribute to.


[1] It’s a bit embarrassing that this “First Classical Postulate,” which Keynes himself said "is the portion of my book which most needs to be revised," is the first positive claim in the book.

[2] Mehrling prefers to trace his intellectual lineage to the independent tradition of American monetary economics of Young, Hansen and Shaw.  But I think the essential content is similar.

Liquidity Preference and Solidity Preference in the 19th Century

So I've been reading Homer and Sylla's History of Interest Rates. One of the many fascinating things I've learned, is that in the market for federal debt, what we today call an inverted yield curve was at one time the norm.

From the book:

Three small loans floated in 1820–1821, principally to permit the continued redemption of high rate war loans, provide an interesting clue to investor preference... These were: 

$4.7 million “5s of 1820,” redeemable in 1832; sold at 100 = 5%.
“6s of 1820,” redeemable at pleasure of United States; sold at 102 = 5.88%.
“5s of 1821,” redeemable in 1835; sold at 1051⁄8 =4.50%, and at 108 = 4.25%. 

The yield was highest for the issue with early redemption risk and much lower for those with later redemption risks.

Nineteenth century government bonds were a bit different from modern bonds, in that the principal was repaid at the option of the borrower; repayment is usually not permitted until a certain date. [1] They were also sold with a fixed yield in terms of face value -- that's what the "5" and "6" refer to -- but the actual yield depended on the discount or premium they were sold at. The important thing for our purposes is that the further away the earliest possible date of repayment is, the lower the interest rate -- the opposite of the modern term premium. That's what the passage above is saying.

The pattern isn't limited to the 1820-21 bonds, either; it seems to exist through most of the 19th century, at least for the US. It's the same with the massive borrowing during the Civil War:

In 1864, although the war was approaching its end, it had only been half financed. The Treasury was able to sell a large volume of bonds, but not at such favorable terms as the market price of its seasoned issues might suggest. Early in the year another $100 million of the 5–20s [bonds with a minimum maturity of 5 years and a maximum of 20] were sold and then a new longer issue was sold as follows: 

1864—$75 million “6s”  redeemable in 1881, tax-exempt; sold at 104.45 = 5.60%. 

The Treasury soon made an attempt to sell 5s, which met with a lukewarm reception. In order to attract investors to the lower rate the Treasury extended the term to redemption from five to ten years and the maturity from twenty to forty years: 

1864—$73 million “5%, 10–40s of 1864,” redeemable 1874, due in 1904, tax-exempt; sold at 100 = 5%.

Isn't that striking? The Treasury couldn't get investors to buy its shorter bonds at an acceptable rate, so they had to issue longer bonds instead. You wouldn't see that story today.

The same pattern continues through the 1870s, with the new loans issue to refinance the Civil War debt. The first issue of bonds, redeemable in five to ten years sold at an interest rate of 5%; the next issue, redeemable in 13-15 years sold at 4.5%; and the last issue, redeemable in 27-29 years, sold at 4%. And it doesn’t seem like this is about expectations of a change in rates, like with a modern inverted yield curve. Investors simply were more worried about being stuck with uninvestable cash than about being stuck with unsaleable securities. This is a case where “solidity preference” dominates liquidity preference.

One possible way of explaining this in terms of Axel Leijonhufvud's explanation of the yield curve.

The conventional story for why long loans normally have higher interest rates than short ones is that longer loans impose greater risks on lenders. They may not be able to convert the loan to cash if they need to make some payment before it matures, and they may suffer a capital loss if interest rates change during the life of the loan. But this can't be the whole story, because short loans create the symmetric risk of not knowing what alternative asset will be available when the loan matures. In the one case, the lender risks a capital loss, but in the other case they risk getting a lower income. Why is "capital uncertainty" a greater concern than "income uncertainty"?

The answer, Leijonhufvud suggests, lies in

Keynes' ... "Vision" of a world in which currently active households must, directly or indirectly, hold their net worth in the form of titles to streams that run beyond their consumption horizon. The duration of the relevant consumption plan is limited by the sad fact that "in the Long Run, we are all dead." But the great bulk of the "Fixed Capital of the modem world" is very long- term in nature and is thus destined to survive the generation which now owns it. This is the basis for the wealth effect of changes in asset values. 

The interesting point about this interpretation of the wealth effect is that it also provides a price-theoretical basis for Keynes' Liquidity Preference theory. ... Keynes' (as well as Hicks') statement of this hypothesis has been repeatedly criticized for not providing any rationale for the presumption that the system as a whole wants to shed "capital uncertainty" rather than "income uncertainty." But Keynes' mortal consumers cannot hold land, buildings, corporate equities, British consols, or other permanent income sources "to maturity." When the representative, risk-averting transactor is nonetheless induced by the productivity of roundabout processes to invest his savings in such income sources, he must be resigned to suffer capital uncertainty. Forward markets will therefore generally show what Hicks called a "constitutional weakness" on the demand side.

I would prefer not to express this in terms of households' consumption plans. And I would emphasize that the problem with wealth in the form of long-lived production processes is not just that it produces income far into the future, but that wealth in this form is always in danger of losing its character as money. Once capital is embodied in a particular production process and the organization that carries it out, it tends to evolve into the means of carrying out that organization's intrinsic purposes, instead of the capital's own self-expansion. But for this purpose, the difference doesn't matter; either way, the problem only arises once you have, as Leijonhufvud puts it, "a system 'tempted' by the profitability of long processes to carry an asset stock which turns over more slowly than [wealth owners] would otherwise want."

The temptation of long-lived production processes is inescapable in modern economies, and explains the constant search for liquidity. But in the pre-industrial United States? I don't think so. Long-lived means of production were much less important, and to the extent they did exist, they weren't an outlet for money-capital. Capital's role in production was to finance stocks of raw materials, goods in process and inventories. There was no such thing, I don't think, as investment by capitalists in long-lived capital goods. And even land -- the long-lived asset in most settings -- was not really an option, since it was abundant. The early United States is something like Samuelson's consumption-loan world, where there is no good way to convert command over current goods into future production. [2] So there is excess demand rather than excess supply for long-lasting sources of income.

The switch over to positive term premiums comes early in the 20th century. By the 1920s, short-term loans in the New York market consistently have lower rates than corporate bonds, and 3-month Treasury bills have rates below longer bonds. Of course the organization of financial markets changed quite a lot in this period too, so one wouldn't want to read too much into this timing. But it is at least consistent with the Leijonhufvud story. Liquidity preference becomes dominant in financial markets only once there has been a decisive shift toward industrial production by long-lived firm using capital-intensive techniques, and once claims on those firms has become a viable outlet for money-capital.

* * *

A few other interesting points about 19th century US interest rates. First, they were remarkably stable, at least before the 1870s. (This fits with the historical material on interest rates that Merijn Knibbe has been presenting in his excellent posts at Real World Economics Review.)

Second, there's no sign of a Fisher equation. Nominal interest rates do not respond to changes in the price level, at all. Homer and Sylla mention that in earlier editions of the book, which dealt less with the 20th century, the concept of a "real" interest rate was not even mentioned.

As you can see from this graph, none of the major inflations or deflations between 1850 and 1960 had any effect on nominal interest rates. The idea that there is a fundamentals-determined "real" interest rate while the nominal rate adjusts in response to changes in the price level, clearly has no relevance outside the past 50 years. (Whether it describes the experience of the past 50 years either is a question for another time.)

Finally, there is no sign of "crowding out" of private by public borrowing. It is true that the federal government did have to pay somewhat higher rates during the periods of heavy borrowing (and of course also political uncertainty) in the War of 1812 and the Civil War. But rates for other borrowers didn't budge. And on the other hand, the surpluses that resulted in the redemption of the entire debt in the 1830s didn't deliver lower rates for other borrowers. Homer and Sylla:

Boston yields were about the same in 1835, when the federal debt was wiped out, as they were in 1830; this reinforces the view that there was little change in going rates of long-term interest during this five- year period of debt redemption.

If government borrowing really raises rates for private borrowers, you ought to see it here, given the absence of a central bank for most of this period and the enormous scale of federal borrowing during the Civil War. But you don't.



[1] It seems that most, though not all, bonds were repaid at the earliest possible redemption date, so it is reasonably similar to the maturity of a modern bond.

[2] Slaves are the big exception. So the obvious test for the argument I am making here would be to find the modern pattern of term premiums in the South. Unfortunately, Homer and Sylla aren't any help on this -- it seems the only local bond markets in this period were in New England.

The Puzzle of Profits

Part II of Capital begins with a puzzle: In markets, commodities are supposed to trade only for other commodities of equal value, yet somehow capitalists end up with more value than they start with.

In the world of simple exchange, money is just a convenience for enabling the exchange of commodities: C-M-C is easier to arrange than C-C. But profit-making business is different: the sequence there is M-C-M'. The capitalist enters the market and buys some commodities for a certain sum of money. Later, he sells some commodities, and has a larger sum of money. This increase -- from M to M' -- is the whole point of being capitalist. But in a world of free market exchange, how can it exist?

Let's put some obvious misunderstandings out of the way. There's nothing mysterious about the fact that people can accomplish things with tools and previously acquired materials that they would be unable to with unaided labor. The problem is not that "capital," in the sense of a stock of tools and materials, is productive in this sense. To the extent that what appears as "profit" in the national accounts is just the cost of replacing worn-out tools and materials, there's no puzzle. [1]

The mystery is, how can someone enter the market with money and, after some series of exchanges, exit with more money? In the sequence M-C-M', how can M' be greater than M? How can the mere possession of money seemingly allow one to acquire more money, seemingly without end?

Before trying to understand Marx's answer, let's consider how non-Marxist economists answer this question.

1. Truck and barter. The most popular answer, among both classical and modern economists, is that the M-C-M' sequence does not exist. All economic activity is aimed at consumption, market exchange is only intended to acquire specific use-values; when you think you see M-C-M you're really looking at part of some C-M-C sequence(s). The classical economists are full of blunt statements that the only possible end of exchange is consumption. In today's economics we find this assumption in the form of the "transversality condition" that says that wealth must go to zero as time goes to infinity. That's right, it is an axiom in modern economics that accumulation cannot be a goal in itself. Or in the words of Simon Wren-Lewis (my new go-to source for the unexamined conventional wisdom of economists): "It would be stupid to accumulate infinite wealth." Well OK then!

2. You earned it. Another answer is that the capitalist brings some additional unmeasured commodity to the production process. They are providing not just money M but also management ability, risk-bearing capacity, etc. In this view, if we correctly measured inputs, we would find that  M'=M. In its most blatantly apologetic form this is effectively skewered by comrades Ackerman and Beggs in the current Jacobin. For unincorporated businesses, it is true, it is not straightforward to distinguish between profits proper and the wages of managerial labor, but that can't account for profits in general, or for the skewed distribution of income across households. If anything, much of what is reported as managerial salaries should probably be called profits. This is a point made in different ways by Piketty and Saez  and Dumenil and Levy; you can also find it offered as straightforward business advice.

3. It was the pictures that got small. The other main classical answer is that profit is the reward for "abstinence" (Senior) or "waiting" (Cassel). (I guess this is also the theory of Bohm-Bawerk and the other Austrians, but I admit I don't know much about that stuff.) It appears today as a discount rate on future consumption. This invites the same question as the first answer: Is capitalist accumulation really motivated by future consumption? It also invites a second question: In what sense is a good tomorrow less valuable than the same good today? Is the utility derived from a glass of wine in 2013 really less than the utility derived from the same glass consumed in 2012,or 2010, or 1995? (So far this has not been my experience.) The logically consistent answer, if you want to defend profit as the return to waiting, is to say Yes. The capital owner's pure time preference then represents an objective inferiority of output at a later date compared with the same output at an earlier date.

This is a logically consistent answer to the profits puzzle, and it could even be true with the right assumptions about the probability of an extinction-event asteroid impact/Khmer Rouge takeover/zombie apocalypse. With a sufficiently high estimate of the probability of some such contingency, M' is really equal to M when discounted appropriately; capitalists aren't really gaining anything when you take into account their odds of being eaten by zombies and/or suffocated by plastic bag, before they get to enjoy their profits. [2]  But I don't think anyone wants to really own this point of view -- to hold it consistently you must believe that economic activity becomes objectively less able to satisfy human needs as time goes by. [3]

4. Oops, underpaid again. We can take the same "profit as reward for waiting" idea, but instead of seeing a pure time preference as consistent with rational behavior, as modern economists (somehow) do, instead interpret it like the classical economists (including Cassel, whose fascinating Nature and Necessity of Interest I just read), as a psychological or sociological phenomenon. Consumption in the future is objectively identical to the same consumption today, but people for some reason fail to assign it the same subjective value it the same. Either they suffer from a lack of "telescopic facility," or, in Cassel's (and Leijonhufvud's) more sophisticated formulation, the discount rate is a reflection of the human life expectancy: People are not motivated to provide for their descendants beyond their children, and future generations are not around to bargain for themselves. Either way, the outcome is that exchange does not happen at value -- production is systematically organized around a higher valuation of goods today than goods tomorrow, even though their actual capacity to provide for satisfaction of human needs is the same. Which implies that workers -- who provide labor today for a good tomorrow -- are systematically underpaid.

5. Property is theft. The last and simplest possibility is that profits are always just rents. Capitalists and workers start out as just "agents" with their respective "endowments." By whatever accident of circumstances, the former just end up underpaying the latter. Maybe they are better informed.

We could develop all these points further -- and will, I hope, in the future. But I want to move on to (my idea of) Marx's answer to the puzzle.

One other thing to clear up first: profit versus interest. Both refer to money tomorrow you receive by virtue of possessing money today. The difference is that in the case of profit, you must purchase and sell commodities in between. What is the relationship between these two forms of income? For someone like Cassel, interest has priority; profit is a derived form combining interest with income from managerial skill and/or a rent. For Marx on the other hand, and also for Smith, Ricardo, etc., profit is the primitive and interest is the derived form; interest is redistribution of profits already earned in production. (Smith: "The interest of money is always a derivative revenue, which, if it is not paid from the profit which is made by the use of the money, must be paid from some other source of revenue.") In other words, are profits an addition to interest, or is interest as a subtraction from profit? For Marx, the latter. The fundamental question is how money profits can arise through exchange of commodities. [4]

Marx gives his answer in chapter four: The capitalist purchases labor-power at its value, but gets the results of the labor expended by that labor-power. The latter exceeds the former. In other words, people are capable of producing more than it takes to reproduce themselves, and that increment is captured by the capitalist. In four hours, you can produce what you need to live on. The next four or six or eight or twelve hours, you are working for The Man.

This is the answer, as Marx gives it. Labor power is paid for at its value. But having purchased labor power, the capitalist now has access to living labor, which can produce more than the the cost of its own reproduction.

I think this is right. But it's not really a satisfactory answer, is it? It's formally correct. But what does it mean?

One way of fleshing it out is to ask: Why is it even possible that labor can produce more than the reproduction-costs of labor power? Think of Ricardo's world. Profits are positive because we have not yet reached the steady state -- there are still natural resources available whose more intensive use will yield a surplus beyond the cost of the labor and capital required to use them. The capitalist captures that surplus because capital has the short side of both markets -- there is currently excess land going unutilized, and excess labor going unutilized. [5]

Another way: There is something in the production process other than exchange, but which is captured via exchange.

I want to think of it this way: Humanity does have the ability to increase social value of output, or in other words the aggregate capacity to satisfy human needs from nature does in general grow over time. This "growth" happens through our collective creative interchange with nature -- it is about pushing into the unknown, a process of discovery -- it is not captured beforehand in the market values of commodities.

In a proper market, you cannot exchange a good in your possession for a good with a greater value, that is, with a greater capacity to satisfy human needs in general. (Your own particular needs, yes.) But you can, through creative activity, through a development of your own potential, increase the general level of satisfaction of human needs. The capitalist by buying labor power at its value, is able to capture this creative increment and call it their private property.

Our potential is realized through a creative interchange with nature. It's not known in advance. What can we do, what can't we do -- we only learn by trying. We push against the world, and discover how the world pushes back, in so doing understand it better and find how it can be reshaped to better suit our needs. Individually or collectively, it's a process of active discovery.

You as a person can exchange the various things you are in possession of, including your labor power, for other things of equal value. (Though for different use values, which are more desired by you.) But you will also discover, through a process of active learning and struggle, what you are capable of, what are the limits of your powers, what creative work you can do that you cannot fully conceive of now.

Through the process of education, you don't just acquire something that you understood clearly at the outset. You transform yourself and learn things you didn't even know you didn't know. When you do creative work you don't know what the finished product will be until you've finished it. I still -- and I hope for the rest of my life -- find myself reading economics and having those aha moments where you say, "oh that's what this debate is all about, I never got it before!" And science and technology above all involve the discovery of new possibilities through a process of active pushing against the limits of our knowledge of the world.

The results of these active process of self-development and exploration form use-values, but they are not commodities. They were not produced for exchange. They were not even known of before they came into being. But while they are not themselves commodities, they are attached to commodities, they cannot be realized except through existing commodities. I may produce in myself, through this process of self-testing, a capacity for musical performance, let's say. But I cannot realize this capacity without, at least, a sufficient claim on my own time, and probably also concrete use-values in the form of an instrument, an appropriate performance space, etc., and also some claim on the time of others. In this case one can imagine acquiring these things individually, but many -- increasingly over time -- processes of self-discovery are inherently collective. Science and technology especially. So specifically a discovery that allows cheaper production of an existing commodity, or the creation of a new commodity with new use-values, can only become become concrete in the hands of those who control the process of production of commodities. By purchasing labor power -- in the market, at its value -- capitalists gain control of the production process. They are thus able to claim the fruits of humanity's collective self-discovery and interchange with nature as their own private property.

In some cases, this is quite literal. Recall Smith's argument that one of the great advantages of the division of labor is that it allows specialized workers to discover improved ways of carrying out their tasks. "A great part of the machines made use of in those manufactures in which labour is most subdivided, were originally the inventions of common workmen, who, being each of them employed in some very simple operation, naturally turned their thoughts towards finding out easier and readier methods of performing it." Who do you think gained the surplus from these inventions? This still happens. Read any good account of work under capitalism, like Barbara Garson's classic books All the Livelong Day and The Electronic Sweatshop. You'll find people actively struggling to do their jobs better -- the customer service representative who wants to get the caller to the person who can actually solve their problem, the bookshelf installer who wants it to fit in the room just right. The results of these struggles are realized as profits for their employers. But these are exceptional. The normal case today is the large-scale collective process of discovery, which is then privately appropriated. Every new technology draws on a vast history of publicly-available scientific work -- sometimes we see this directly as with biomedical research, but even when it's not so obvious it's still there. Every Hollywood movie draws on a vast collective project of storytelling, a general collective effort to imbue certain symbols with meaning. Again see this most directly in the movies that draw on folktales and other public-domain work, but it's true generically.

It is this vast collective effort at transformation of nature and ourselves that allows the value of output to be greater than the value of what existed before it. Without it, we would eventually reach the classical steady state where the exercise of labor could produce no more than the value of the labor power that yielded it. So when Marx says the source of profits is the fact that labor can produce more than the value of labor power, lying behind this is the fact that, due to humanity's collective creative efforts, we are continuing to find new ways to shape the world to our use.

Capital is coordination before it is tangible means of production. Initially (logically and historically) the capitalist simply occupies a strategic point in exchange between independent producers thanks to the possession of liquid wealth; but as the extension of the division of labor requires more detailed coordination between the separate producers, the capitalist takes over a more direct role in managing production itself. "That a capitalist should command on the field of production, is now as indispensable as that a general should command on the field of battle."

There is another way of looking at this: in terms of the extension of cooperation and the division of labor, which is realized in and through capitalist production, but in principle is independent of it. I'll take this up in a following post.


[1] Marx makes this point clearly in his critique of the Gotha program.  Elimination of surplus as such cannot be a goal of socialism.

[2] It would seem that we have enough evidence to rule out a sufficiently high probability of world-ending catastrophe to explain observed interest rates, assuming the minimum possible return on accumulated wealth is zero. But of course in some conceivable circumstances it could be negative -- that's why I include the Khmer Rouge takeover, where your chance of summary execution is presumably positively related to your accumulated wealth. Also, maybe we have reason to think that  catastrophe is more likely in the future than we would naively infer from the past. It would be funny if someone tried to explain interest rates in terms of the doomsday argument.

[3] There has been a lot of discussion of appropriate social discount rates in the context of climate change. But nobody in that debate, as far as I can tell, takes the logical next step of arguing that excessively high discount rates imply a comprehensive market failure, not just with respect to climate change. There is not a special social discount rate for climate, there is an appropriate social discount rate for all future costs and benefits. If market interest rates are not the right tool for weighing current costs against future benefits for climate, they are not the right guide for anything, including the market activities where they currently govern.

[4] Yes, interest exists independently of profits from production, and indeed is much older. Marx recognizes this. But capitalism is not generalized usury.

[5]  And substitution between factors is impossible -- Marx's "iron law of proportions" -- or at least limited.

Aggregate Demand and Modern Macro

Start with a point on language.

People often talk about aggregate demand as if it were a quantity. But this is not exactly right. There's no number or set of numbers in the national accounts labeled "aggregate demand". Rather, aggregate demand is a way of interpreting the numbers in the national accounts. (Admittedly, it's the way of interpreting them that guided their creation in the first place). It's a statement about a relationship between economic quantities. Specifically, it's a statement that we should think about current income and current expenditure as mutually determining each other.

This way of thinking is logically incompatible with the way macroeconomics is taught in (almost) all graduate programs today, which is in terms of optimization under an intertemporal budget constraint. I'll avoid semi-pejorative terms like mainstream and neoclassical, and instead follow Robert Gordon and call this approach modern macro.

In the Keynesian income-expenditure vision -- which today survives only, as Leijonhufvud put it, "in the Hades of undergraduate instruction" -- we think of economic actors as making decisions about current spending in terms of current receipts. If I earn $X, I will spend $Y; if I earn one dollar more, I'll spend so many additional cents. We can add detail by breaking these income and expenditure flows in various ways -- income from dividends vs. incomes from wages, income to someone at the top decile vs someone at the bottom, income to urban households vs income to rural ones; and expenditures on services, durable goods, taxes, etc., which generate income in their turn. This is the way macro forecasting models used by business and government were traditionally constructed, and may still be for all I know.

Again, these are relationships; they tell us that for any given level of aggregate money income, there is a corresponding level of aggregate expenditure. The level of income that is actually realized, is the one for which desired expenditure just equals income. And if someone for whatever reason adjusts their desired level of expenditure at that income, the realized level of income will change in the same direction, by a greater or lesser extent. (This is the multiplier.)

I should stress that while this way of thinking may imply or suggest concrete predictions, these are not themselves empirical claims, but logical relationships.

The intertemporal optimization approach followed in modern macro is based on a different set of logical relationships. In this framework, agents know their endowments and tastes (and everyone else's, though usually in these models agents are assumed to be identical) and the available production technology in all future periods. So they know all possible mixes of consumption and leisure available to them over the entire future and the utility each provides. Based on this knowledge they pick, for all periods simultaneously ("on the 8th day of creation" -- that's Leijonhufvud again) the optimal path of labor, output and consumption.

I realize that to non-economists this looks very strange. I want to stress, I'm not giving a dismissive or hostile summary. To anyone who's done economics graduate work in the last 15 or 20 years (a few heterodox enclaves excepted) constructing models like this is just what "doing macroeconomics" means.

(For a concrete example, a first-year grad textbook offers as one of its first exercises in thinking like an economist the question of why countries often run current account deficits in wartime. The answer is entirely in terms of why countries would choose to allocate a greater share of consumption to periods when there is war, and how interest rates adjust to make this happen. The possibility that war leads to higher incomes and expenditure, some of which inevitably falls on imported goods -- the natural answer in the income-expenditure framework -- is not even mentioned. Incidentally, as this example suggests, thinking in terms of intertemporal allocation is not always necessarily wrong.)

In these models, there is no special relationship between income and expenditure flows just because they happen to take place at the same time or in any particular order. The choice between jam today and jam tomorrow is no different from the choice between blackberry and lingonberry jam, and the checks you get from your current job and from the job you'll hold ten years from now are no more different than the checks from two different jobs that you hold right now are. Over one year or 50, the problem is simply the best allocation of your total income over your possible consumption baskets -- subject, of course, to various constraints which may make the optimal allocation unachievable.

My point here is not that modern models are unrealistic. I am perfectly happy to stipulate that the realism of assumptions doesn't matter. Models are tools for logical analysis, not toy train sets -- they don't have to look like real economies to be useful.

(Although I do have to point out that modern macroeconomics models are often defended precisely on the grounds of microfoundations -- i.e. more realistic assumptions. But it is simply not true that modern models are more "microfounded" than income-expenditure ones in any normal English sense. Microfoundations does not mean, as you might imagine, that a model has an explicit story about the individual agents in the economy and how they make choices -- the old Keynesian models do at least as well as the modern ones by that standard. Rather, microfoundations means that the agents' choices consist of optimizing some quantity under true -- i.e. model consistent -- expectations.)

But again, I come not to bury or dispraise modern models. My point is just that they are logically incompatible with the concept of aggregate demand. It's not that modern macroeconomists believe that aggregate demand is unimportant, it's that within their framework those words don't mean anything. Carefully written macro papers don't even footnote it as a minor factor that can be ignored. Even something anodyne like "demand might also play a role" would come across like the guy in that comic who asks the engineers if they've "considered logarithms" to help with cooling.

The atomic units of one vision are flows -- that is, money per time period -- between economic units. The atomic units of the other are prices and quantities of different goods. Any particular empirical question can be addressed within either vision. But they generate very different intuitions, and ideas of what questions are most important. 

Still, it is true that the same concrete phenomena can be described in either language. The IS curve is the obvious example. In the Hades of the undergraduate classroom we get the old Keynesian story of changes in interest rate changing desired aggregate expenditure at each given income. While in the sunlit Arcadia of graduate classes, the same relationship between interest rates and current expenditure is derived explicitly from intertemporal optimization.

So what's the problem, you say. If either language can be used to describe the same phenomena, why not use the same language as the vast majority of other economists?

This is a serious question, and those of us who want to do macro without DSGE models need a real answer for it. My answer is that default assumptions matter. Yes, with the right tweaks the two models can be brought to a middle ground, with roughly the same mix of effects from the current state and expected future states of the world. But even if you can get agreement on certain concrete predictions, you won't agree on what parts of them depend on the hard core of your theory and what on more or less ad hoc auxiliary assumptions. So Occam's Razor will cut in opposite directions -- a change that simplifies the story from one perspective, is adding complexity from the other.

For example, from the income-expenditure perspective, saying that future interest rates will have a similar effect on current activity as current interest rates do, is a strong additional assumption. Whereas from the modern perspective, it's saying that they don't have similar effects that is the additional assumption that needs to be explained. Or again, taking an example with concrete applications to teaching, the most natural way to think about interest rates and exchange rates in the income-expenditure vision is in terms of how the the flow of foreign investment responds to interest rates differentials. Whereas in the modern perspective -- which is now infiltrating even the underworld -- the most natural way is in terms of rational agents' optimal asset mix, taking into account the true expected values of future exchange rates and interest rates.

Or, what got me thinking about this in the first place. I've been reading a lot of empirical work on credit constraints and business investment in the Great Recession -- I might do a post on it in the next week or so, though an academic style literature review seems a bit dull even for this blog -- and three things have become clear.

First, the commitment to intertemporal optimization means that New Keynesians really need financial frictions. In a world where current output is an important factor in investment, where investment spending is linked to profit income, and where expectations are an independently adjusting variable, it's no problem to have a slowdown in investment triggered by fall in demand in some other sector, by a fall in the profit share, or by beliefs about the future becoming more pessimistic. But in the modern consensus, the optimal capital stock is determined by the fundamental parameters of the model and known to all agents, so you need a more or less permanent fall in the return on investment, due presumably to some negative technological shock or bad government policy. Liberal economists hate this stuff, but in an important sense it's just a logical application of the models they all teach. If in all your graduate classes you talk about investment and growth in terms of the technologically-determined marginal product of capital, you can hardly blame people when, faced with a slowdown in investment and growth, they figure that's the first place to look. The alternative is some constraint that prevents firms from moving toward their desired capital stock, which really has to be a financial friction of some kind. For the older Keynesian perspective credit constraints are one possible reason among others for a non-supply-side determined fall in investment; for the modern perspective they're the only game in town.

Second, the persistence of slumps is a problem for them in a way that it's not in the income-expenditure approach. Like the previous point, this follows from the fundamental fact that in the modern approach, while there can be constraints that prevent desired expenditure from being achieved, there's never causation from actual expenditure to desired expenditure. Businesses know, based on fundamentals, their optimal capital stock, and choose an investment path that gets them there while minimizing adjustment costs. Similarly, households know their lifetime income and utility-maximizing consumption path. Credit constraints may hold down investment or consumption in one period, but once they're relaxed, desired expenditure will be as high or higher than before. So you need persistent constraints to explain persistently depressed spending. Whereas in the income-expenditure model there is no puzzle. Depressed investment in one period directly reduces investment demand in the next period, both by reducing capacity utilization and by reducing the flow of profit income. If your core vision of the economy is a market, optimizing the allocation of scare resources, then if that optimal allocation isn't being achieved there must be some ongoing obstacle to trade. Whereas if you think of the economy in terms of income and expenditure flows, it seems perfectly natural that an interruption to some flow will will disrupt the pattern, and once the obstacle is removed the pattern will return to its only form only slowly if at all.

And third: Only conservative economists acknowledge this theoretical divide. You can find John Cochrane writing very clearly about alternative perspectives in macro. But saltwater economists -- and the best ones are often the worst in this respect -- are scrupulously atheoretical. I suspect this is because they know that if they wanted to describe their material in a more general way, they'd have to use the language of intertemporal optimization, and they are smart enough to know what a tar baby that is. So they become pure empiricists.

In Leon Fink's wonderful history of the New York health care workers' union 1199, Upheaval in the Quiet Zone, he talks about how the union's early leaders and activists were disproportionately drawn from Communist Party members and sympathizers, and other leftists. Like other communist-led unions, 1199 was kicked out of the CIO in the 1940s, but unlike most of the others, it didn't fade into obscurity. Originally a drugstore-employees union, it led the new wave of organizing of health care and public employees in the 1960s. Fink attributes a large part of its unusual commitment to organizing non-white and female workers, in an explicitly civil-rights framework, and its unusual lack of corruption and venality, to the continued solidarity of the generation of the 1930s. Their shared political commitments were a powerful source of coordination and discipline. But, says Fink, it was impossible for them to pass these commitments on to the next generation. Yes, in 1199, unlike most other unions, individual leftists were not purged; but there was still no organized left, either within the union or in connection to a broader movement. So there was no way for the first generation to reproduce themselves, and as they retired 1199 became exposed to the same pressures that produced conservative, self-serving leadership in so many other unions.

I feel there's something similar going on in economics. There are plenty of people at mainstream departments with a basically Keynesian vision of the economy. But they write and, especially, teach in a language that is basically alien to that vision. They're not reproducing the capacity for their own thought. They're running a kind of intellectual extractive industry, mining older traditions for insights but doing nothing to maintain them.

I had this conversation with a friend at a top department the other day:

me: http://noahpinionblog.blogspot.com/2013/03/the-swamp-of-dsge-despair.html

  what do you think? is this kind of critique valid/useful?

11:17 AM him: its totally true

11:18 AM and you wouldn't know what was getting baked into the cake unless you were trained in the literature

  I only started understanding the New Keynsian models a little while ago

  and just had the lazy "they are too complicated" criticism

11:19 AM now I understand that they are stupidly too complicated (as Noah's post points out)

11:20 AM me: so what is one supposed to do?

  if this is the state of macro

 him: i dunno. I think participating in this literature is a fucking horror show

 me: but you don't like heterodox people either, so....?

11:21 AM him: maybe become a historian

  or figure out some simple variant of the DSGEmodels that you can make your point and publish empirical stuff

This is where so many smart people I know end up. You have to use mainstream models -- you can't move the profession or help shape policy (or get a good job) otherwise. But on many questions, using those models means, at best, contorting your argument into a forced and unnatural framework, with arbitrary-seeming assumptions doing a lot of the work; at worst it means wading head-deep into an intellectual swamp. So you do some mix of what my friend suggests here: find a version of the modern framework that is loose enough to cram your ideas into without too much buckling; or give up on telling a coherent story about the world and become a pure empiricist. (Or give up on economics.) But either way, your insights about the world have to come from somewhere else. And that's the problem, because insight isn't cheap. The line I hear so often -- let's master mainstream methods so we can better promote our ideas -- assumes you've already got all your ideas, so the only work left is publicity.

If we want to take questions of aggregate demand and everything that goes with it -- booms, crises, slumps -- seriously, then we need a theoretical framework in which those questions arise naturally.


[*] Keynes' original term was "effective demand." The two are interchangeable today. But it's interesting to read the original passages in the GT. While they are confusingly written, there's no question that Keynes' meant "effective" in the sense of "being in effect." That is, of many possible levels of demand possible in an economy, which do we actually see? This is different from the way the term is usually understood, as "having effect," that is, backed with money. Demand backed with money is, of course, simply demand.  


UPDATE: The Cochrane post linked above is really good, very worth reading. It gives more of the specific flavor of these models than I do. He writes: In Old Keynesian models,

consumption depends on today's income through the "marginal propensity to consume" mpc. 

Modern new-Keynesian models are utterly different from this traditional view. Lots of people, especially in policy, commentary, and blogging circles, like to wave their hands over the equations of new Keynesian models and claim they provide formal cover for traditional old-Keynesian intuition, with all the optimization, budget constraints, and market clearing conditions that the old-Keynesian analysis never really got right taken care of. A quick look at our equations and the underlying logic shows that this is absolutely not the case.  

Consider how lowering interest rates is supposed to help. In the old Keynesian model, investment I = I(r) responds to lower interest rates, output and income Y = C + I + G, so rising investment raises income, which raises consumption in (4), which raises income some more, and so on. By contrast, the simple new-Keynesian model needs no investment, and interest rates simply rearrange consumption demand over time. 

Similarly, consider how raising government spending is supposed to help. In the old Keynesian model,  raising G in Y = C + I + G raises Y, which raises consumption C by (4), which raises Y some more, and so on. In the new-Keynesian model, the big multiplier comes because raising government spending raises inflation, which lowers interest rates, and once again brings consumption forward in time.

Note, for example, that in a standard New Keynesian model, expected future interest rates enter into current consumption exactly as the present interest rate does. This will obviously shape people's intuitions about things like the effectiveness of forward guidance by the Fed.


UPDATE 2: As usual, this blog is just an updated, but otherwise much inferior, version of What Leijonhufvud Said. From his 2006 essay The Uses of the Past:

We should expect to find an ahistorical attitude among a group of scientists busily soling puzzles within an agreed-upon paradigm... Preoccupation with the past is then a diversion or a luxury. When things are going well it is full steam ahead! .... As long as "normal" progress continues to be made in the established directions, there is no need to reexamine the past... 

Things begin to look different if and when the workable vein runs out or, to change the metaphor, when the road that took you to the "frontier of the field" ends in a swamp or in a blind alley. A lot of them do. Our fads run out and we get stuck. Reactions to finding yourself in a cul-de-sac differ. Tenured professors might be content to accommodate themselves to it, spend their time tidying up the place, putting in modern conveniences... Braver souls will want out and see a tremendous leap of the creative imagination as the only way out -- a prescription, however, that will leave ordinary mortals just climbing the walls. Another way to go is to backtrack. Back there, in the past, there were forks in the road and it is possible, even probable, that some roads were more promising than the one that looked most promising at the time...

This is exactly the spirit in which I'm trying to rehabilitate postwar income-expenditure Keynesianism. The whole essay is very worth reading, if you're interest at all in the history of economic thought.

Reviving the Knife-Edge: Aggregate Demand in the Long Run

The second issue of the new Review of Keynesian Economics is out, this one focused on growth. [1] There's a bunch of interesting contributions, but I especially like the piece by Steve Fazzari, Pietro Ferri, Edward Greenberg and Anna Maria Variato, on growth and aggregate demand.

The starting point is the familiar puzzle that we have a clear short-run story in which changes in output  [2] on the scale of the business cycle are determined by aggregate demand -- that is, by changes in desired expenditure relative to income. But we don't have a story about what role, if any, aggregate demand plays in the longer run.

The dominant answer -- unquestioned in the mainstream [3], but also widespread among heterodox writers -- is, it doesn't. Economic growth is supposed to depend on a different set of factors -- technological change, population growth and capital accumulation -- than those that influence demand in the short run. But it's not obvious how you get from the short-run to the long -- what mechanism, if any, that ensures that the various demand-driven fluctuations will converge to the long-run path dictated by these "fundamentals"?

This is the question posed by Fazzari et al., building on Roy Harrod's famous 1939 article. As Harrod noted, there are two relations between investment and output: investment influences output as a source of demand in the short run, and in the longer run higher output induces investment in order to maintain a stable capital-output ratio. More investment boosts growth, for the first channel, the multiplier; growth induces investment, through the second, the accelerator. With appropriate assumptions you can figure out what combinations of growth and investment satisfy both conditions. Harrod called the corresponding growth paths the "warranted" rate of growth. The problem is, as Harrod discovered, these combinations are dynamically unstable -- if growth strays just a bit above the warranted level, it will accelerate without limit; if falls a little below the warranted rate, it will keep falling til output is zero. 

This is Harrod's famous "knife-edge." It's been almost entirely displaced from the mainstream by Solow type growth models. Solow argued that the dynamic instability of Harrod's model was due to the assumption of a fixed target capital-output ratio, and that the instability goes away if capital and labor are smoothly substitutible. In fact, Harrod makes no such assumption -- his 1939 article explicitly considers the possibility that capitalists might target different capital-output ratios based on factors like interest rates. More generally, Solow didn't resolve the problem of how short-run demand dynamics converge to the long-run supply-determined growth path, he just assumed it away. 

The old textbook solution was price flexibility. Demand constraints are supposed to only exist because prices are slow to adjust, so given enough time for prices to reach market-clearing levels, aggregate demand should cease to exist. The obvious problem with this, as Keynes already observed, is that while flexible prices may help to restore equilibrium in individual markets, they operate in the wrong direction for output as a whole. A severe demand shortfall tends to produce deflation, which further reduces demand for goods and services; similarly, excessive demand leads to inflation, which tends -- though less certainly -- to further increase demand. As Leijonhufvud notes, it's a weird irony that sticky wages and/or prices are held to be the condition of effective demand failures, when the biggest demand failure of them all, the Depression, saw the sharpest falls in both wages and prices on record. 

The idea that if it just runs its course, deflation -- via the real balance effect or some such -- will eventually restore full employment is too much even for most economists to swallow. So the new consensus replaces price level adjustment with central bank following a policy rule. In textbooks, this is glossed as just hastening an adjustment that would have happened on its own via the price level, but that's obviously backward. When an economy actually does develop high inflation or deflation, central banks consider their jobs more urgent, not less so. It's worth pausing a moment to think about this. While the central bank policy rule is blandly presented as just another equation in a macroeconomic model, the implications are actually quite radical. Making monetary policy the sole mechanism by which the economy converges to full employment (or the NAIRU) implicitly concedes that on its own, the capitalist economy is fundamentally unstable. 

While the question of how, or whether, aggregate demand dynamics converge to a long-run growth path has been ignored or papered over by the mainstream, it gets plenty of attention from heterodox macro. Even in this one issue of ROKE, there are several articles that engage with it in one way or another. The usual answer, among those who do at least ask the question, is that the knife-edge result must be wrong, and indicates some flaw in the way Harrod posed the problem. After all, in real-world capitalist economies, output appears only moderately unstable. Many different adjustments have been proposed to his model to make demand converge to a stable path.

Fazzari et al.'s answer to the puzzle, which I personally find persuasive, is that demand dynamics really are that unstable -- that taken on their own the positive feedbacks between income, expenditure and investment would cause output to spiral toward infinity or fall to zero. The reasons this doesn't happen is because of the ceiling imposed by supply constraints and the the floor set by autonomous expenditure (government spending, long-term investment, exports, etc.). But in general, the level of output is set by expenditure, and there is no reason to expect desired expenditure to converge to exactly full utilization of the economy's resources. When rising demand hits supply constraints, it can't settle at full employment, since in general full employment is only reached on the (unfulfillable) expectation of more-than-full employment. 

Upward demand instability can drive demand to a level that fully employs labor resources. But the full employment path is not stable. ... The system bounces off the ceiling onto an unstable declining growth path.

I won't go through the math, which in any case isn't complicated -- is trivial, even, by the standards of "real" economics papers. The key assumptions are just a sufficiently strong link between income and consumption, and a target capital output ratio, which investment is set to maintain. These two assumptions together define the multiplier-accelerator model; because Fazzari et al explicitly incorporate short-term expectations, they need a third assumption, that unexpected changes in output growth cause expectations of future growth to adjust in the same direction -- in other words, if growth is higher than expected this period, people adjust their estimates of next period's growth upward. These three assumptions, regardless of specific parameter values, are enough to yield dynamic instability, where any deviation from the unique stable growth path tends to amplify over time.

The formal model here is not new. What's more unusual is Fazzari et al.'s suggestion that this really is how capitalist economies behave. The great majority of the time, output is governed only by aggregate demand, and demand is either accelerating or decelerating. Only the existence of expenditure not linked to market income prevents output from falling to zero in recessions; supply constraints -- the productive capacity of the economy -- matters only occasionally, at the peaks of businesses cycles.

Still, one might say that if business-cycle peaks are growing along a supply-determined path, then isn't the New Consensus right to say that the long run trajectory of the economy is governed only by the supply side, technology and all that? Well, maybe -- but even if so,this would still be a useful contribution in giving a more realistic account of how short-term fluctuations add up to long-run path. It's important here that the vision is not of fluctuations around the full-employment level of output, as in the mainstream, but at levels more or less below it, as in the older Keynesian vision. (DeLong at least has expressed doubts about whether the old Keynsians might not have been right on this point.) Moreover, there's no guarantee that actual output will spend a fixed proportion of time at potential, or reach it at all. It's perfectly possible for the inherent instability of the demand process to produce a downturn before supply constraints are ever reached. Financial instability can also lead to a recession before supply constraints are reached (altho more often, I think, the role of financial instability is to amplify a downturn that is triggered by something else.)

So: why do I like this paper so much?

First, most obviously, because I think it's right. I think the vision of cycles and crises as endogenous to the growth process, indeed constitutive of it, is a better, more productive way to think about the evolution of output than a stable equilibrium growth path occasionally disturbed by exogenous shocks. The idea of accelerating demand growth that sooner or later hits supply constraints in a more or less violent crisis, is just how the macroeconomy looks. Consider the most obvious example, unemployment:

What we don't see here, is a stable path with normally distributed disturbances around it. Rather, we see  unemployment falling steadily in expansions and then abruptly reversing to large rises in recessions. To monetarists, the fact that short-run output changes are distributed bimodally, with the economy almost always in a clear expansion or clear recession with nothing in between, is a sign that the business cycle must be the Fed's fault. To me, it's more natural to think that the nonexistence of "mini-recessions" is telling us something about the dynamics of the economic process itself -- that capitalist growth, like love, 

is a growing, or full constant light,
And his first minute, after noon, is night.

Second, I like the argument that output is demand-constrained at almost all times. There is no equilibrium between "aggregate supply" and "aggregate demand"; rather, under normal conditions the supply side doesn't play any role at all. Except for World War II, basically, supply constraints only come into play momentarily at the top of expansions, and not in the form of some kind of equilibration via prices, but as a more or less violent external interruption in the dynamics of aggregate demand. It is more or less always true, that if you ask why is output higher than it was last period, the answer is that someone decided to increase their expenditure. 

Third, I like that the article is picking up the conversation from the postwar Keynesians like Harrod, Kaldor and Hicks, and more recent structural-Keynesian approaches. The fundamental units of the argument are the aggregate behavior of firms and households, without the usual crippling insistence on reducing everything to a problem of intertemporal optimization. (The question of microfoundations gets a one-sentence footnote, which is about what it deserves.) Without getting into these methodological debates here, I think this kind of structuralist approach is one of the most productive ways forward for positive macroeconomic theory. Admittedly, almost all the other papers in this issue of ROKE are coming from more or less the same place, but I single out Fazzari for praise here because he's a legitimate big-name economist -- his best known work was coauthored with Glenn Hubbard. (Yes, that Glenn Hubbard.)

Fourth, I like the paper's notion of economies having different regimes, some of persistently excess demand, some persistent demand shortfalls. When I was talking about this paper with Arjun the other day he asked, very sensibly, what's the relevance to our current situation. My first response was not much, it's more theoretical. But it occurs to me now that the mainstream model (often implicit) of fluctuations around a supply-determined growth path is actually quite important to liberal ideas about fiscal policy. The idea that a deep recession now will be balanced by a big boom sometime in the future underwrites the idea that short-run stimulus should be combined with a commitment to long-run austerity. If, on the other hand, you think that the fundamental parameters of an economy can lead to demand either falling persistently behind, or running persistently ahead, of supply constraints, then you are more likely to think that a deep recession is a sign that fiscal policy is secularly too tight (or investment secularly too low, etc.) So the current relevance of the Fazzari paper is that if you prefer their vision to the mainstream's, you are more likely to see the need for bigger deficits today as evidence of a need for bigger deficits forever.

Finally, on a more meta level, I share the implicit vision of capitalism not as a single system in (or perhaps out of) equilibrium, but involving a number of independent processes which sometimes happen to behave consistently with each other and sometimes don't. In the Harrod story, it's demand-driven output and the productive capacity of the economy, and population growth in particular; one could tell the same story about trade flows and financial flows, or about fixed costs and the degree of monopoly (as Bruce Wilder and I were discussing in comments). Or perhaps borrowing and interest rates. In all cases these are two distinct causal systems, which interact in various ways but are not automatically balanced by any kind of price or equivalent mechanism. The different systems may happen to move together in a way that facilitates smooth growth; or they may move inconsistently, which will bring various buffers into play and, when these are exhausted, lead to some kind of crisis whose resolution lies outside the model.

A few points, not so much of criticism, as suggestions for further development.

First, a minor point -- the assumption that expectations adjust in the same direction as errors is a bit trickier than they acknowledge. I think it's entirely reasonable here, but it's clearly not always valid and the domain over which it applies isn't obvious. If for instance the evolution of output is believed to follow a process like yt = c + alpha t + et, then unusually high growth in one period would lead to expectations of lower growth in the next period, not higher as Fazzari et al assume. And of course to the extent that such expectations would tend to stabilize the path of output, they would be self-fulfilling. (In other words, widespread belief in the mainstream view of growth will actually make the mainstream view more true -- though evidently not true enough.) As I say, I don't think it's a problem here, but the existence of both kinds of expectations is important. The classic historical example is the gold standard: Before WWI, when there was a strong expectation that the gold link would be maintained, a fall in a country's currency would lead to expectations of subsequent appreciation, which produced a capital inflow that in fact led to the appreciation;  whereas after the war, when devaluations seemed more likely, speculative capital flows tended to be destabilizing.

Two more substantive points concern supply constraints. I think it's a strength, not a weakness of the paper that it doesn't try to represent supply constraints in any systematic way, but just leaves them exogenous. Models are tools for logical argument, not toy train sets; the goal is to clarify a particular set of causal relationships, not to construct a miniature replica of the whole economy. Still, there are a couple issues around the relationship between rising demand and supply constraints that one would like to develop further.

First, what concretely happens when aggregate expenditure exceeds supply? It's not enough to just say "it can't," in part because expenditure is in dollar terms while supply constraints represent real physical or sociological limits. As Fazzari et al. acknowledge, we need some Marx with our Keynes here -- we need to bring in falling profits as a key channel by which supply constraints bind. [4] As potential output is approached, there's an increase in the share claimed by inelastically-supplied factors, especially labor, and a fall in the share going to capital. This is the classic Marxian cyclical profit squeeze, though in recent cycles it may be the rents claimed by suppliers of oil and "land" in general, as opposed to wages, that is doing much of the squeezing. But in any case, a natural next step for this work would be to give a more concrete account of the mechanisms by which supply constraints bind. This will also help clarify why the transitions from expansion to recession are so much more abrupt than the transitions the other way. (Just as there are no mini-recessions, neither are there anti-crises.) The pure demand story explains why output cannot rise stably on the full employment trajectory, but must either rise faster or else fall; but on its own it's essentially symmetrical and can't explain why recessions are so much steeper and shorter than expansions. Minsky-type dynamics, where a fall in output means financial commitments cannot be met, must also play a role here.

Second, how does demand-driven evolution of output affect growth of supply? They write, 

while in our simple model the supply-side path is assumed exogenous, it is easy to posit realistic economic channels through which the actual demand-determined performance of the economy away from full employment affects conditions of supply. The quantity and productivity of labor and capital at occasional business-cycle peaks will likely depend on the demand-determined performance of the economy in the normal case in which the system is below full employment.

I think this is right, and a very important point to develop. There is increasing recognition in the mainstream of the importance of hysteresis -- the negative effects on economic potential of prolonged unemployment. There's little or no discussion of anti-hysteresis -- the possibility that inflationary booms have long-term positive effects on aggregate supply. But I think it would be easy to defend the argument that a disproportionate share of innovation, new investment and laborforce broadening happens in periods when demand is persistently pushing against potential. In either case, the conventional relationship between demand and supply is reversed -- in a world where (anti-)hysteresis is important, "excessive" demand may lead to only temporarily higher inflation but permanently higher employment and output, and conversely.

Finally, obsessive that I am, I'd like to link this argument to Leijonhufvud's notion of a "corridor of stability" in capitalist economies, which -- though Leijonhufvud isn't cited -- this article could be seen as a natural development of. His corridor is different from this one, though -- it refers to the relative stability of growth between crises. The key factor in maintaining that stability is the weakness of the link between income and expenditure as long as changes in income remain small. Within some limits, changes in the income of households and firms do not cause them to revise their beliefs about future income (expectations are normally fairly inelastic), and can be buffered by stocks of liquid assets and the credit system. Only when income diverges too far from its prior trajectory do expectations change -- often discontinuously -- and, if the divergence is downward, do credit constraints being to bind. If it weren't for these stabilizing factors, capitalist growth would always, and not just occasionally, take the form of explosive bubbles. 

Combining Leijonhufvud and Fazzari et al., we could envision the capitalist growth path passing through concentric bands of stability and instability. The innermost band is Leijonhufvud's corridor, where the income-expenditure link is weak. Outside of that is the band of Harrodian instability, where expectations are adjusting and credit constraints bind. That normal limits of that band are set, at least over most of the postwar era, by active stabilization measures by the state, meaning in recent decades monetary policy. (The signature of this is that recoveries from recessions are very rapid.) Beyond this is the broader zone of instability described by the Fazzari paper -- though keeping the 1930s in mind, we might emphasize the zero lower bound on gross investment a bit more, and autonomous spending less, in setting the floor of this band. And beyond that must be a final zone of instability where the system blows itself to pieces.

Bottom line: If heterodox macroeconomic theory is going to move away from pure critique (and it really needs to) and focus on developing a positive alternative to the mainstream, articles like this are a very good start.

[1] It's unfortunate that no effort has been made to make ROKE content available online. Since neither of the universities I'm affiliated with has a subscription yet, it's literally impossible for me -- and presumably you -- to see most of the articles. I imagine this is a common problem for new journals. When I raised this issue with one of the editors, and asked if they'd considered an open-access model, he dismissed the idea and suggested I buy a subscription -- hey, it's only $80 for students. I admit this annoyed me some. Isn't it self-defeating to go to the effort of starting a new journal and solicit lots of great work for it, and then shrug off responsibility for ensuring that people can actually read it?

[2] It's not a straightforward question what exactly is growing in economic growth. When I talk about demand dynamics, I prefer to use the generic term "activity," as proxied by a variety of measures like GDP, employment, capacity utilization, etc. (This is also how NBER business-cycle dating works.) But here I'll follow Fazzari et al. and talk about output, presumably the stuff measured by GDP.

[3] See for instance this post from David Altig at the Atlanta Fed, from just yesterday: 

Forecasters, no matter where they think that potential GDP line might be, all believe actual GDP will eventually move back to it. "Output gaps"—the shaded area representing the cumulative miss of actual GDP relative to its potential—simply won't last forever. And if that means GDP growth has to accelerate in the future (as it does when GDP today is below its potential)—well, that's just the way it is.

Here we have the consensus with no hedging. Everyone knows that long-run growth is independent of aggregate demand, so slower growth today means faster growth tomorrow. That's "nature," that's just the way it is.

[4] This fits with the story in Capitalism Since 1945, still perhaps the first book I would recommend to anyone trying to understand the evolution of modern economies. From the book:

The basic idea of overaccumulation is that capitalism sometimes generates a higher rate of accumulation than can be sustained, and thus the rate of accumulation has eventually to fall. Towards the end of the postwar boom, an imbalance between accumulation and the labor supply led to increasingly severe labor shortage. ... Real wages were pulled up and older machines rendered unprofitable, allowing a faster transfer of workers to new machines. This could in principle have occurred smoothly: as profitability slid down, accumulation could have declined gently to a sustainable rate. but the capitalist system has no mechanism guaranteeing a smooth transition in such circumstances. In the late sixties the initial effect of overaccumulation was a period of feverish growth with rapidly rising wages and prices and an enthusiasm for get-rich-quick schemes. These temporarily masked, but could not suppress, the deterioration in profitability. Confidence was undermined, investment collapsed and a spectacular crash occurred. Overaccumulation gave rise, not to a mild decline in the profit rate, but to a classic capitalist crisis.

I think the Marxist framework here, with its focus on profit rates, complements rather than contradicts the Keynesian frame of Fazzari et al. and its focus on demand. In particular, the concrete mechanisms by which supply constraints operate are much clearer here.