Update (6/18/2019): The current draft of my paper is now available on SSRN. Here is a link.
The annual meeting of the History of Economics Society is coming up in two weeks. It will be held at Columbia University at New York, and I will be presenting an unpublished paper of mine “Say’s Law and the Classical Theory of Depressions.” I began writing this paper about 20 years ago, but never finished it. My thinking about Say’s Law goes back to my first paper on classical monetary theory, and I have previously written blog-posts about Say’s Law (here and here). And more recently I realized that in a temporary-equilibrium framework, both Say’s Law and Walras’s Law, however understood, may be violated.
Here’s the abstract from my paper:
Say’s Law occupies a prominent, but equivocal, position in the history of economics, having been the object of repeated controversies about its meaning and significance since it was first propounded early in the nineteenth century. It has been variously defined, and arguments about its meaning and validity have not reached consensus about what was being attacked or defended. This paper proposes a unifying interpretation of Say’s Law based on the idea that the monetary sector of an economy with a competitively supplied money involves at least two distinct markets not just one. Thus, contrary to the Lange-Patinkin interpretation of Say’s Law, an excess supply or demand for money does not necessarily imply an excess supply or demand for goods in a Walrasian GE model. Beyond modifying the standard interpretation of the inconsistency between Say’s Law and a monetary economy, the paper challenges another standard interpretation of Say’s Law as being empirically refuted by the existence of lapses from full employment and economic depressions. Under the alternative interpretation, originally suggested by Clower and Leijonhufvud and by Hutt, Say’s Law provides a theory whereby disequilibrium in one market, causing the amount actually supplied to fall short of what had been planned to be supplied, reduces demand in other markets, initiating a cumulative process of shrinking demand and supply. This cumulative process of contracting supply is analogous to the Keynesian multiplier whereby a reduction in demand initiates a cumulative process of declining demand. Finally, it is shown that in a temporary-equilibrium context, Walras’s Law (and a fortiori Say’ Law) may be violated.
Here is the Introduction of my paper.
I. Introduction
Say’s Law occupies a prominent, but uncertain, position in the history of economics, having been the object of repeated controversies since the early nineteenth century. Despite a formidable secondary literature, the recurring controversies still demand a clear resolution. Say’s Law has been variously defined, and arguments about its meaning and validity have failed to achieve any clear consensus about just what is being defended or attacked. So, I propose in this paper to reconsider Say’s Law in a way that is faithful in spirit to how it was understood by its principal architects, J. B. Say, James Mill, and David Ricardo as well as their contemporary critics, and to provide a conceptual framework within which to assess the views of subsequent commentators.
In doing so, I hope to dispel perhaps the oldest and certainly the most enduring misunderstanding about Say’s Law: that it somehow was meant to assert that depressions cannot occur, or that they are necessarily self-correcting if market forces are allowed to operate freely. As I have tried to suggest with the title of this paper, Say’s Law was actually an element of Classical insights into the causes of depressions. Indeed, a version of the same idea expressed by Say’s Law implicitly underlies those modern explanations of depressions that emphasize coordination failures, though Say’s Law actually conveys an additional insight missing from most modern explanations.
The conception of Say’s Law articulated in this paper bears a strong resemblance to what Clower (1965, 1967) and Leijonhufvud (1968, 1981) called Say’s Principle. However, their artificial distinction between Say’s Law and Say’s Principle suggests a narrower conception and application of Say’s principle than, I believe, is warranted. Moreover, their apparent endorsement of the idea that the validity of Say’s Law somehow depends in a critical way on the absence of money implied a straightforward misinterpretation of Say’s Law earlier propounded by, among other, Hayek, Lange and Patinkin in which only what became known as Walras’s Law and not Say’s Law is a logically necessary property of a general-equilibrium system. Finally, it is appropriate to note at the outset that, in most respects, the conception of Say’s Law for which I shall be arguing was anticipated in a quirky, but unjustly neglected, work by Hutt (1975) and by the important, and similarly neglected, work of Earl Thompson (1974).
In the next section, I offer a restatement of the Classical conception of Say’s Law. That conception was indeed based on the insight that, in the now familiar formulation, supply creates its own demand. But to grasp how this insight was originally understood, one must first understand the problem for which Say’s Law was proposed as a solution. The problem concerns the relationship between a depression and a general glut of all goods, but it has two aspects. First, is a depression in some sense caused by a general glut of all goods? Second, is a general glut of all goods logically conceivable in a market economy? In section three, I shall consider the Classical objections to Say’s Law and the responses offered by the Classical originators of the doctrine in reply to those objections. In section four, I discuss the modern objections offered to Say’s Law, their relation to the earlier objections, and the validity of the modern objections to the doctrine. In section five, I re-examine the Classical doctrine, relating it explicitly to a theory of depressions characterized by “inadequate aggregate demand.” I also elaborate on the subtle, but important, differences between my understanding of Say’s Law and what Clower and Leijonhufvud have called Say’s Principle. In section six, I show that when considered in the context of a temporary-equilibrium model in there is an incomplete set of forward and state-contingent markets, not even Walras’s Law, let alone Say’s Law, is logically necessary property of the model. An understanding of the conditions in which neither Walras’s Law nor Say’s Law is satisfied provides an important insight into financial crises and the systemic coordination failures that are characteristic of the deep depression to which they lead.
And here are the last two sections of the paper.
VI. Say’s Law Violated
I have just argued that Clower, Leijonhufvud and Hutt explained in detail how the insight provided by Say’s Law into the mechanism whereby disturbances causing disequilibrium in one market or sector can be propagated and amplified into broader and deeper economy-wide disturbances and disequilibria. I now want to argue that by relaxing the strict Walrasian framework in which since Lange (1942) articulated Walras’s Law and Say’s Law, it is possible to show conditions under which neither Walras’s Law nor Say’s Law is satisfied.
I relax the Walrasian framework by assuming that there is not a complete set of forward and state-contingent markets in which future transactions can be undertaken in the present. Because there a complete set of markets in which future prices are determined and visible to everyone, economic agents must formulate their intertemporal plans for production and consumption relying not only on observed current prices, but also on their expectations of currently unobservable future prices. As already noted, the standard proof of Walras’s Law and a fortiori of Say’s Law (or Identity) are premised on the assumption that all agents make their decisions about purchases and sales on their common knowledge of all prices.
Thus, in the temporary-equilibrium framework, economic agents make their production and consumption decisions not on the basis of their common knowledge of future market prices common, but on their own conjectural expectations of those prices, expectations that may, or may not, be correct, and may, or may not, be aligned with the expectations of other agents. Unless the agents’ expectations of future prices are aligned, the expectations of some, or all, agents must be disappointed, and the plans to buy and sell formulated based on those expectations will have to be revised, or abandoned, once agents realize that their expectations were incorrect.
Consider a simple two-person, two-good, two-period model in which agents make plans based on current prices observed in period 1 and their expectations of what prices will be in period 2. Given price expectations for period 2, period-1 prices are determined in a tatonnement process, so that no trading occurs until a temporary- equilibrium price vector for period 1 is found. Assume, further, that price expectations for period 2 do not change in the course of the tatonnement. Once a period-1 equilibrium price vector is found, the two budget constraints subject to which the agents make their optimal decisions, need not have the same values for expected prices in period 2, because it is not assumed that the period-2 price expectations of the two agents are aligned. Because the proof of Walras’s Law depends on agents basing their decisions to buy and sell each commodity on prices for each commodity in each period that are common to both agents, Walras’s Law cannot be proved unless the period-2 price expectations of both agents are aligned.
The implication of the potential violation of Walras’s Law is that when actual prices turn out to be different from what they were expected to be, economic agents who previously assumed obligations that are about to come due may be unable to discharge those obligations. In standard general-equilibrium models, the tatonnement process assures that no trading takes place unless equilibrium prices have been identified. But in a temporary-equilibrium model, when decisions to purchase and sell are based not on equilibrium prices, but on actual prices that may not have been expected, the discharge of commitments is not certain.
Of course, if Walras’s Law cannot be proved, neither can Say’s Law. Supply cannot create demand when the insolvency of economic agents obstructs mutually advantageous transactions between agents when some agents have negative net worth. The negative net worth of some agents can be transmitted to other agents holding obligations undertaken by agents whose net worth has become negative.
Moreover, because the private supply of a medium of exchange by banks depends on the value of money-backing assets held by banks, the monetary system may cease to function in an economy in which the net worth of agents whose obligations are held banks becomes negative. Thus, the argument made in section IV.A for the validity of Say’s Law in the Identity sense breaks down once a sufficient number of agents no longer have positive net worth.
VII. Conclusion
My aim in this paper has been to explain and clarify a number of the different ways in which Say’s Law has been understood and misunderstood. A fair reading of the primary and secondary literature allows one to understand that many of the criticisms of Say’s Law have been not properly understood the argument that Say’s Law was either intended or could be reasonably interpreted to have said. Indeed, Say’s Law, properly understood, can actually help one understand the cumulative process of economic contraction whose existence supposedly proved its invalidity. However, I have also been able to show that there are plausible conditions in which a sufficiently serious financial breakdown, associated with financial crises in which substantial losses of net worth lead to widespread and contagious insolvency, when even Walras’s Law, and a fortiori Say’s Law, no longer hold. Understanding how Say’s Law may be violated may thus help in understanding the dynamics of financial crises and the cumulative systemic coordination failures of deep depressions.
I will soon be posting the paper on SSRN. When it’s posted I will post a link to an update to this post.
Uneasy Money 