Archive for the 'Keynes' Category

Krugman on Minsky, IS-LM and Temporary Equilibrium

Catching up on my blog reading, I found this one from Paul Krugman from almost two weeks ago defending the IS-LM model against Hyman Minsky’s criticism (channeled by his student Lars Syll) that IS-LM misrepresented the message of Keynes’s General Theory. That is an old debate, and it’s a debate that will never be resolved because IS-LM is a nice way of incorporating monetary effects into the pure income-expenditure model that was the basis of Keynes’s multiplier analysis and his policy prescriptions. On the other hand, the model leaves out much of what most interesting and insightful in the General Theory – precisely the stuff that could not easily be distilled into a simple analytic model.

Here’s Krugman:

Lars Syll approvingly quotes Hyman Minsky denouncing IS-LM analysis as an “obfuscation” of Keynes; Brad DeLong disagrees. As you might guess, so do I.

There are really two questions here. The less important is whether something like IS-LM — a static, equilibrium analysis of output and employment that takes expectations and financial conditions as given — does violence to the spirit of Keynes. Why isn’t this all that important? Because Keynes was a smart guy, not a prophet. The General Theory is interesting and inspiring, but not holy writ.

It’s also a protean work that contains a lot of different ideas, not necessarily consistent with each other. Still, when I read Minsky putting into Keynes’s mouth the claim that

Only a theory that was explicitly cyclical and overtly financial was capable of being useful

I have to wonder whether he really read the book! As I read the General Theory — and I’ve read it carefully — one of Keynes’s central insights was precisely that you wanted to step back from thinking about the business cycle. Previous thinkers had focused all their energy on trying to explain booms and busts; Keynes argued that the real thing that needed explanation was the way the economy seemed to spend prolonged periods in a state of underemployment:

[I]t is an outstanding characteristic of the economic system in which we live that, whilst it is subject to severe fluctuations in respect of output and employment, it is not violently unstable. Indeed it seems capable of remaining in a chronic condition of subnormal activity for a considerable period without any marked tendency either towards recovery or towards complete collapse.

So Keynes started with a, yes, equilibrium model of a depressed economy. He then went on to offer thoughts about how changes in animal spirits could alter this equilibrium; but he waited until Chapter 22 (!) to sketch out a story about the business cycle, and made it clear that this was not the centerpiece of his theory. Yes, I know that he later wrote an article claiming that it was all about the instability of expectations, but the book is what changed economics, and that’s not what it says.

This all seems pretty sensible to me. Nevertheless, there is so much in the General Theory — both good and bad – that isn’t reflected in IS-LM, that to reduce the General Theory to IS-LM is a kind of misrepresentation. And to be fair, Hicks himself acknowledged that IS-LM was merely a way of representing one critical difference in the assumptions underlying the Keynesian and the “Classical” analyses of macroeconomic equilibrium.

But I would take issue with the following assertion by Krugman.

The point is that Keynes very much made use of the method of temporary equilibrium — interpreting the state of the economy in the short run as if it were a static equilibrium with a lot of stuff taken provisionally as given — as a way to clarify thought. And the larger point is that he was right to do this.

When people like me use something like IS-LM, we’re not imagining that the IS curve is fixed in position for ever after. It’s a ceteris paribus thing, just like supply and demand. Assuming short-run equilibrium in some things — in this case interest rates and output — doesn’t mean that you’ve forgotten that things change, it’s just a way to clarify your thought. And the truth is that people who try to think in terms of everything being dynamic all at once almost always end up either confused or engaging in a lot of implicit theorizing they don’t even realize they’re doing.

When I think of a temporary equilibrium, the most important – indeed the defining — characteristic of that temporary equilibrium is that expectations of at least some agents have been disappointed. The disappointment of expectations is likely to, but does not strictly require, a revision of disappointed expectations and of the plans conditioned on those expectations. The revision of expectations and plans as a result of expectations being disappointed is what gives rise to a dynamic adjustment process. But that is precisely what is excluded from – or at least not explicitly taken into account by – the IS-LM model. There is nothing in the IS-LM model that provides any direct insight into the process by which expectations are revised as a result of being disappointed. That Keynes could so easily think in terms of a depressed economy being in equilibrium suggests to me that he was missing what I regard as the key insight of the temporary-equilibrium method.

Of course, there are those who argue, perhaps most notably Roger Farmer, that economies have multiple equilibria, each with different levels of output and employment corresponding to different expectational parameters. That seems to me a more Keynesian approach, an approach recognizing that expectations can be self-fulfilling, than the temporary-equilibrium approach in which the focus is on mistaken and conflicting expectations, not their self-fulfillment.

Now to be fair, I have to admit that Hicks, himself, who introduced the temporary-equilibrium approach in Value and Capital (1939) later (1965) suggested in Capital and Growth (p. 65) that both the Keynes in the General Theory and the temporary-equilibrium approach of Value and Capital were “quasi-static.” The analysis of the General Theory “is not the analysis of a process; no means has been provided by which we can pass from one Keynesian period to the next. . . . The Temporary Equilibrium model of Value and Capital, also, is quasi-static in just the same sense. The reason why I was contented with such a model was because I had my eyes fixed on Keynes.

Despite Hicks’s identification of the temporary-equilibrium method with Keynes’s method in the General Theory, I think that Hicks was overly modest in assessing his own contribution in Value and Capital, failing to appreciate the full significance of the method he had introduced. Which, I suppose, just goes to show that you can’t assume that the person who invents a concept or an idea is necessarily the one who has the best, or most comprehensive, understanding of what the concept means of what its significance is.

The Trouble with IS-LM (and its Successors)

Lately, I have been reading a paper by Roger Backhouse and David Laidler, “What Was Lost with IS-LM” (an earlier version is available here) which was part of a very interesting symposium of 11 papers on the IS-LM model published as a supplement to the 2004 volume of History of Political Economy. The main thesis of the paper is that the IS-LM model, like the General Theory of which it is a partial and imperfect distillation, aborted a number of promising developments in the rapidly developing, but still nascent, field of macroeconomics in the 1920 and 1930s, developments that just might, had they not been elbowed aside by the IS-LM model, have evolved into a more useful and relevant theory of macroeconomic fluctuations and policy than we now possess. Even though I have occasionally sparred with Scott Sumner about IS-LM – with me pushing back a bit at Scott’s attacks on IS-LM — I have a lot of sympathy for the Backhouse-Laidler thesis.

The Backhouse-Laidler paper is too long to summarize, but I will just note that there are four types of loss that they attribute to IS-LM, which are all, more or less, derivative of the static equilibrium character of Keynes’s analytic method in both the General Theory and the IS-LM construction.

1 The loss of dynamic analysis. IS-LM is a single-period model.

2 The loss of intertemporal choice and expectations. Intertemporal choice and expectations are excluded a priori in a single-period model.

3 The loss of policy regimes. In a single-period model, policy is a one-time affair. The problem of setting up a regime that leads to optimal results over time doesn’t arise.

4 The loss of intertemporal coordination failures. Another concept that is irrelevant in a one-period model.

There was one particular passage that I found especially impressive. Commenting on the lack of any systematic dynamic analysis in the GT, Backhouse and Laidler observe,

[A]lthough [Keynes] made many remarks that could be (and in some cases were later) turned into dynamic models, the emphasis of the General Theory was nevertheless on unemployment as an equilibrium phenomenon.

Dynamic accounts of how money wages might affect employment were only a little more integrated into Keynes’s formal analysis than they were later into IS-LM. Far more significant for the development in Keynes’s thought is how Keynes himself systematically neglected dynamic factors that had been discussed in previous explanations of unemployment. This was a feature of the General Theory remarked on by Bertil Ohlin (1937, 235-36):

Keynes’s theoretical system . . . is equally “old-fashioned” in the second respect which characterizes recent economic theory – namely, the attempt to break away from an explanation of economic events by means of orthodox equilibrium constructions. No other analysis of trade fluctuations in recent years – with the possible exception of the Mises-Hayek school – follows such conservative lines in this respect. In fact, Keynes is much more of an “equilibrium theorist” than such economists as Cassel and, I think, Marshall.

Backhouse and Laidler go on to cite the Stockholm School (of which Ohlin was a leading figure) as an example of explicitly dynamic analysis.

As Bjorn Hansson (1982) has shown, this group developed an explicit method, using the idea of a succession of “unit periods,” in which each period began with agents having plans based on newly formed expectations about the outcome of executing them, and ended with the economy in some new situation that was the outcome of executing them, and ended with the economy in some new situation that was the outcome of market processes set in motion by the incompatibility of those plans, and in which expectations had been reformulated, too, in the light of experience. They applied this method to the construction of a wide variety of what they called “model sequences,” many of which involved downward spirals in economic activity at whose very heart lay rising unemployment. This is not the place to discuss the vexed question of the extent to which some of this work anticipated the Keynesian multiplier process, but it should be noted that, in IS-LM, it is the limit to which such processes move, rather than the time path they follow to get there, that is emphasized.

The Stockholm method seems to me exactly the right way to explain business-cycle downturns. In normal times, there is a rough – certainly not perfect, but good enough — correspondence of expectations among agents. That correspondence of expectations implies that the individual plans contingent on those expectations will be more or less compatible with one another. Surprises happen; here and there people are disappointed and regret past decisions, but, on the whole, they are able to adjust as needed to muddle through. There is usually enough flexibility in a system to allow most people to adjust their plans in response to unforeseen circumstances, so that the disappointment of some expectations doesn’t become contagious, causing a systemic crisis.

But when there is some sort of major shock – and it can only be a shock if it is unforeseen – the system may not be able to adjust. Instead, the disappointment of expectations becomes contagious. If my customers aren’t able to sell their products, I may not be able to sell mine. Expectations are like networks. If there is a breakdown at some point in the network, the whole network may collapse or malfunction. Because expectations and plans fit together in interlocking networks, it is possible that even a disturbance at one point in the network can cascade over an increasingly wide group of agents, leading to something like a system-wide breakdown, a financial crisis or a depression.

But the “problem” with the Stockholm method was that it was open-ended. It could offer only “a wide variety” of “model sequences,” without specifying a determinate solution. It was just this gap in the Stockholm approach that Keynes was able to fill. He provided a determinate equilibrium, “the limit to which the Stockholm model sequences would move, rather than the time path they follow to get there.” A messy, but insightful, approach to explaining the phenomenon of downward spirals in economic activity coupled with rising unemployment was cast aside in favor of the neater, simpler approach of Keynes. No wonder Ohlin sounds annoyed in his comment, quoted by Backhouse and Laidler, about Keynes. Tractability trumped insight.

Unfortunately, that is still the case today. Open-ended models of the sort that the Stockholm School tried to develop still cannot compete with the RBC and DSGE models that have displaced IS-LM and now dominate modern macroeconomics. The basic idea that modern economies form networks, and that networks have properties that are not reducible to just the nodes forming them has yet to penetrate the trained intuition of modern macroeconomists. Otherwise, how would it have been possible to imagine that a macroeconomic model could consist of a single representative agent? And just because modern macroeconomists have expanded their models to include more than a single representative agent doesn’t mean that the intellectual gap evidenced by the introduction of representative-agent models into macroeconomic discourse has been closed.

How to Think about Own Rates of Interest, Version 2.0

In my previous post, I tried to explain how to think about own rates of interest. Unfortunately, I made a careless error in calculating the own rate of interest in the simple example I constructed to capture the essence of Sraffa’s own-rate argument against Hayek’s notion of the natural rate of interest. But sometimes these little slip-ups can be educational, so I am going to try to turn my conceptual misstep to advantage in working through and amplifying the example I presented last time.

But before I reproduce the passage from Sraffa’s review that will serve as our basic text in this post as it did in the previous post, I want to clarify another point. The own rate of interest for a commodity may be calculated in terms of any standard of value. If I borrow wheat and promise to repay in wheat, the wheat own rate of interest may be calculated in terms of wheat or in terms of any other standard; all of those rates are own rates, but each is expressed in terms of a different standard.

Lend me 100 bushels of wheat today, and I will pay you back 102 bushels next year. The own rate of interest for wheat in terms of wheat would be 2%. Alternatively, I could borrow $100 of wheat today and promise to pay back $102 of wheat next year. The own rate of interest for wheat in terms of wheat and the own rate of interest for wheat in terms of dollars would be equal if and only if the forward dollar price of wheat is the same as the current dollar price of wheat. The commodity or asset in terms of which a price is quoted or in terms of which we measure the own rate is known as the numeraire. (If all that Sraffa was trying to say in criticizing Hayek was that there are many equivalent ways of expressing own interest rates, he was making a trivial point. Perhaps Hayek didn’t understand that trivial point, in which case the rough treatment he got from Sraffa was not undeserved. But it seems clear that Sraffa was trying — unsuccessfully — to make a more substantive point than that.)

In principle, there is a separate own rate of interest for every commodity and for every numeraire. If there are n commodities, there are n potential numeraires, and n own rates can be expressed in terms of each numeraire. So there are n-squared own rates. Each own rate can be thought of as equilibrating the demand for loans made in terms of a given commodity and a given numeraire. But arbitrage constraints tightly link all these separate own rates together. If it were cheaper to borrow in terms of one commodity than another, or in terms of one numeraire than another, borrowers would switch to the commodity and numeraire with the lowest cost of borrowing, and if it were more profitable to lend in terms of one commodity, or in terms of one numeraire, than another, lenders would switch to lending in terms of the commodity or numeraire with the highest return.

Thus, competition tends to equalize own rates across all commodities and across all numeraires. Of course, perfect arbitrage requires the existence of forward markets in which to contract today for the purchase or sale of a commodity at a future date. When forward markets don’t exist, some traders may anticipate advantages to borrowing or lending in terms of particular commodities based on their expectations of future prices for those commodities. The arbitrage constraint on the variation of interest rates was discovered and explained by Irving Fisher in his great work Appreciation and Interest.

It is clear that if the unit of length were changed and its change were foreknown, contracts would be modified accordingly. Suppose a yard were defined (as once it probably was) to be the length of the king’s girdle, and suppose the king to be a child. Everybody would then know that the “yard” would increase with age and a merchant who should agree to deliver 1000 “yards” ten years hence, would make his terms correspond to his expectations. To alter the mode of measurement does not alter the actual quantities involved but merely the numbers by which they are represented. (p. 1)

We thus see that the farmer who contracts a mortgage in gold is, if the interest is properly adjusted, no worse and no better off than if his contract were in a “wheat” standard or a “multiple” standard. (p. 16)

I pause to make a subtle, but, I think, an important, point. Although the relationship between the spot and the forward price of any commodity tightly constrains the own rate for that commodity, the spot/forward relationship does not determine the own rate of interest for that commodity. There is always some “real” rate reflecting a rate of intertemporal exchange that is consistent with intertemporal equilibrium. Given such an intertemporal rate of exchange — a real rate of interest — the spot/forward relationship for a commodity in terms of a numeraire pins down the own rate for that commodity in terms of that numeraire.

OK with that introduction out of the way, let’s go back to my previous post in which I wrote the following:

Sraffa correctly noted that arbitrage would force the terms of such a loan (i.e., the own rate of interest) to equal the ratio of the current forward price of the commodity to its current spot price, buying spot and selling forward being essentially equivalent to borrowing and repaying.

That statement now seems quite wrong to me. Sraffa did not assert that arbitrage would force the own rate of interest to equal the ratio of the spot and forward prices. He merely noted that in a stationary equilibrium with equality between all spot and forward prices, all own interest rates would be equal. I criticized him for failing to note that in a stationary equilibrium all own rates would be zero. The conclusion that all own rates would be zero in a stationary equilibrium might in fact be valid, but if it is, it is not as obviously valid as I suggested, and my criticism of Sraffa and Ludwig von Mises for not drawing what seemed to me an obvious inference was not justified. To conclude that own rates are zero in a stationary equilibrium, you would, at a minimum, have to show that there is at least one commodity which could be carried from one period to the next at a non-negative profit. Sraffa may have come close to suggesting such an assumption in the passage in which he explains how borrowing to buy cotton spot and immediately selling cotton forward can be viewed as the equivalent of contracting a loan in terms of cotton, but he did not make that assumption explicitly. In any event, I mistakenly interpreted him to be saying that the ratio of the spot and forward prices is the same as the own interest rate, which is neither true nor what Sraffa meant.

And now let’s finally go back to the key quotation of Sraffa’s that I tried unsuccessfully to parse in my previous post.

Suppose there is a change in the distribution of demand between various commodities; immediately some will rise in price, and others will fall; the market will expect that, after a certain time, the supply of the former will increase, and the supply of the latter fall, and accordingly the forward price, for the date on which equilibrium is expected to be restored, will be below the spot price in the case of the former and above it in the case of the latter; in other words, the rate of interest on the former will be higher than on the latter. (“Dr. Hayek on Money and Capital,” p. 50)

In my previous post I tried to flesh out Sraffa’s example by supposing that, in the stationary equilibrium before the demand shift, tomatoes and cucumbers were both selling for a dollar each. In a stationary equilibrium, tomato and cucumber prices would remain, indefinitely into the future, at a dollar each. A shift in demand from tomatoes to cucumbers upsets the equilibrium, causing the price of tomatoes to fall to, say, $.90 and the price of cucumbers to rise to, say, $1.10. But Sraffa also argued that the prices of tomatoes and cucumbers would diverge only temporarily from their equilibrium values, implicitly assuming that the long-run supply curves of both tomatoes and cucumbers are horizontal at a price of $1 per unit.

I misunderstood Sraffa to be saying that the ratio of the future price and the spot price of tomatoes equals one plus the own rate on tomatoes. I therefore incorrectly calculated the own rate on tomatoes as 1/.9 minus one or 11.1%. There were two mistakes. First, I incorrectly inferred that equality of all spot and forward prices implies that the real rate must be zero, and second, as Nick Edmunds pointed out in his comment, a forward price exceeding the spot price would actually be reflected in an own rate less than the zero real rate that I had been posited. To calculate the own rate on tomatoes, I ought to have taken the ratio of spot price to the forward price — (.9/1) — and subtracted one plus the real rate. If the real rate is zero, then the implied own rate is .9 minus 1, or -10%.

To see where this comes from, we can take the simple algebra from Fisher (pp. 8-9). Let i be the interest rate calculated in terms of one commodity and one numeraire, and j be the rate of interest calculated in terms of a different commodity in that numeraire. Further, let a be the rate at which the second commodity appreciates relative to the first commodity. We have the following relationship derived from the arbitrage condition.

(1 + i) = (1 + j)(1 + a)

Now in our case, we are trying to calculate the own rate on tomatoes given that tomatoes are expected (an expectation reflected in the forward price of tomatoes) to appreciate by 10% from $.90 to $1.00 over the term of the loan. To keep the analysis simple, assume that i is zero. Although I concede that a positive real rate may be consistent with the stationary equilibrium that I, following Sraffa, have assumed, a zero real rate is certainly not an implausible assumption, and no important conclusions of this discussion hinge on assuming that i is zero.

To apply Fisher’s framework to Sraffa’s example, we need only substitute the ratio of the forward price of tomatoes to the spot price — [p(fwd)/p(spot)] — for the appreciation factor (1 + a).

So, in place of the previous equation, I can now substitute the following equivalent equation:

(1 + i) = (1 + j) [p(fwd)/p(spot)].

Rearranging, we get:

[p(spot)/p(fwd)] (1 + i) = (1 + j).

If i = 0, the following equation results:

[p(spot)/p(fwd)] = (1 + j).

In other words:

j = [p(spot)/p(fwd)] – 1.

If the ratio of the spot to the forward price is .9, then the own rate on tomatoes, j, equals -10%.

My assertion in the previous post that the own rate on cucumbers would be negative by the amount of expected depreciation (from $1.10 to $1) in the next period was also backwards. The own rate on cucumbers would have to exceed the zero equilibrium real rate by as much as cucumbers would depreciate at the time of repayment. So, for cucumbers, j would equal 11%.

Just to elaborate further, let’s assume that there is a third commodity, onions, and that, in the initial equilibrium, the unit prices of onions, tomatoes and cucumbers are equal. If the demand shift from tomatoes to cucumbers does not affect the demand for onions, then, even after the shift in demand, the price of onions will remain one dollar per onion.

The table below shows prices and own rates for tomatoes, cucumbers and onions for each possible choice of numeraire. If prices are quoted in tomatoes, the price of tomatoes is fixed at 1. Given a zero real rate, the own rate on tomatoes in period is zero. What about the own rate on cucumbers? In period 0, with no change in prices expected, the own rate on cucumbers is also zero. However in period 1, after the price of cucumbers has risen to 1.22 tomatoes, the own rate on cucumbers must reflect the expected reduction in the price of a cucumber in terms of tomatoes from 1.22 tomatoes in period 1 to 1 tomato in period 2, a price reduction of 22% percent in terms of tomatoes, implying a cucumber own rate of 22% in terms of tomatoes. Similarly, the onion own rate in terms of tomatoes would be 11% percent reflecting a forward price for onions in terms of tomatoes 11% below the spot price for onions in terms of tomatoes. If prices were quoted in terms of cucumbers, the cucumber own rate would be zero, and because the prices of tomatoes and onions would be expected to rise in terms of cucumbers, the tomato and onion own rates would be negative (-18.2% for tomatoes and -10% for onions). And if prices were quoted in terms of onions, the onion own rate would be zero, while the tomato own rate, given the expected appreciation of tomatoes in terms of onions, would be negative (-10%), and the cucumber own rate, given the expected depreciation of cucumbers in terms of onions, would be positive (10%).

own_rates_in_terms_of_tomatoes_cucumbers_onions

The next table, summarizing the first one, is a 3 by 3 matrix showing each of the nine possible combinations of numeraires and corresponding own rates.

own_rates_in_terms_of_tomatoes_cucumbers_onions_2

Thus, although the own rates of the different commodities differ, and although the commodity own rates differ depending on the choice of numeraire, the cost of borrowing (and the return to lending) is equal regardless of which commodity and which numeraire is chosen. As I stated in my previous post, Sraffa believed that, by showing that own rates can diverge, he showed that Hayek’s concept of a natural rate of interest was a nonsense notion. However, the differences in own rates, as Fisher had already showed 36 years earlier, are purely nominal. The underlying real rate, under Sraffa’s own analysis, is independent of the own rates.

Moreover, as I pointed out in my previous post, though the point was made in the context of a confused exposition of own rates,  whenever the own rate for a commodity is negative, there is an incentive to hold it now for sale in the next period at a higher price it would fetch in the current period. It is therefore only possible to observe negative own rates on commodities that are costly to store. Only if the cost of holding a commodity is greater than its expected appreciation would it not be profitable to withhold the commodity from sale this period and to sell instead in the following period. The rate of appreciation of a commodity cannot exceed the cost of storing it (as a percentage of its price).

What do I conclude from all this? That neither Sraffa nor Hayek adequately understood Fisher. Sraffa seems to have argued that there would be multiple real own rates of interest in disequilibrium — or at least his discussion of own rates seem to suggest that that is what he thought — while Hayek failed to see that there could be multiple nominal own rates. Fisher provided a definitive exposition of the distinction between real and nominal rates that encompasses both own rates and money rates of interest.

A. C. Pigou, the great and devoted student of Alfred Marshall, and ultimately his successor at Cambridge, is supposed to have said “It’s all in Marshall.” Well, one could also say “it’s all in Fisher.” Keynes, despite going out of his way in Chapter 12 of the General Theory to criticize Fisher’s distinction between the real and nominal rates of interest, actually vindicated Fisher’s distinction in his exposition of own rates in Chapter 17 of the GT, providing a valuable extension of Fisher’s analysis, but apparently failing to see the connection between his discussion and Fisher’s, and instead crediting Sraffa for introducing the own-rate analysis, even as he undermined Sraffa’s ambiguous suggestion that real own rates could differ. Go figure.

How to Think about Own Rates of Interest

Phil Pilkington has responded to my post about the latest version of my paper (co-authored by Paul Zimmerman) on the Sraffa-Hayek debate about the natural rate of interest. For those of you who haven’t been following my posts on the subject, here’s a quick review. Almost three years ago I wrote a post refuting Sraffa’s argument that Hayek’s concept of the natural rate of interest is incoherent, there being a multiplicity of own rates of interest in a barter economy (Hayek’s benchmark for the rate of interest undisturbed by monetary influences), which makes it impossible to identify any particular own rate as the natural rate of interest.

Sraffa maintained that if there are many own rates of interest in a barter economy, none of them having a claim to priority over the others, then Hayek had no basis for singling out any particular one of them as the natural rate and holding it up as the benchmark rate to guide monetary policy. I pointed out that Ludwig Lachmann had answered Sraffa’s attack (about 20 years too late) by explaining that even though there could be many own rates for individual commodities, all own rates are related by the condition that the cost of borrowing in terms of all commodities would be equalized, differences in own rates reflecting merely differences in expected appreciation or depreciation of the different commodities. Different own rates are simply different nominal rates; there is a unique real own rate, a point demonstrated by Irving Fisher in 1896 in Appreciation and Interest.

Let me pause here for a moment to explain what is meant by an own rate of interest. It is simply the name for the rate of interest corresponding to a loan contracted in terms of a particular commodity, the borrower receiving the commodity now and repaying the lender with the same commodity when the term of the loan expires. Sraffa correctly noted that in equilibrium arbitrage would force the terms of such a loan (i.e., the own rate of interest) to equal the ratio of the current forward price of the commodity to its current spot price, buying spot and selling forward being essentially equivalent to borrowing and repaying.

Now what is tricky about Sraffa’s argument against Hayek is that he actually acknowledges at the beginning of his argument that in a stationary equilibrium, presumably meaning that prices remain at their current equilibrium levels over time, all own rates would be equal. In fact if prices remain (and are expected to remain) constant period after period, the ratio of forward to spot prices would equal unity for all commodities implying that the natural rate of interest would be zero. Sraffa did not make that point explicitly, but it seems to be a necessary implication of his analysis. (This implication seems to bear on an old controversy in the theory of capital and interest, which is whether the rate of interest would be positive in a stationary equilibrium with constant real income). Schumpeter argued that the equilibrium rate of interest would be zero, and von Mises argued that it would be positive, because time preference implying that the rate of interest is necessarily always positive is a kind of a priori praxeological law of nature, the sort of apodictic gibberish to which von Mises was regrettably predisposed. The own-rate analysis supports Schumpeter against Mises.

So to make the case against Hayek, Sraffa had to posit a change, a shift in demand from one product to another, that disrupts the pre-existing equilibrium. Here is the key passage from Sraffa:

Suppose there is a change in the distribution of demand between various commodities; immediately some will rise in price, and others will fall; the market will expect that, after a certain time, the supply of the former will increase, and the supply of the latter fall, and accordingly the forward price, for the date on which equilibrium is expected to be restored, will be below the spot price in the case of the former and above it in the case of the latter; in other words, the rate of interest on the former will be higher than on the latter. (p. 50)

This is a difficult passage, and in previous posts, and in my paper with Zimmerman, I did not try to parse this passage. But I am going to parse it now. Assume that demand shifts from tomatoes to cucumbers. In the original equilibrium, let the prices of both be $1 a pound. With a zero own rate of interest in terms of both tomatoes and cucumbers, you could borrow a pound of tomatoes today and discharge your debt by repaying the lender a pound of tomatoes at the expiration of the loan. However, after the demand shift, the price of tomatoes falls to, say, $0.90 a pound, and the price of cucumbers rises to, say, $1.10 a pound. Sraffa posits that the price changes are temporary, not because the demand shift is temporary, but because the supply curves of tomatoes and cucumbers are perfectly elastic at $1 a pound. However, supply does not adjust immediately, so Sraffa believes that there can be a temporary deviation from the long-run equilibrium prices of tomatoes and cucumbers.

The ratio of the forward prices to the spot prices tells you what the own rates are for tomatoes and cucumbers. For tomatoes, the ratio is 1/.9, implying an own rate of 11.1%. For cucumbers the ratio is 1/1.1, implying an own rate of -9.1%. Other prices have not changed, so all other own rates remain at 0. Having shown that own rates can diverge, Sraffa thinks that he has proven Hayek’s concept of a natural rate of interest to be a nonsense notion. He was mistaken.

There are at least two mistakes. First, the negative own rate on cucumbers simply means that no one will lend in terms of cucumbers for negative interest when other commodities allow lending at zero interest. It also means that no one will hold cucumbers in this period to sell at a lower price in the next period than the cucumbers would fetch in the current period. Cucumbers are a bad investment, promising a negative return; any lending and investing will be conducted in terms of some other commodity. The negative own rate on cucumbers signifies a kind of corner solution, reflecting the impossibility of transporting next period’s cucumbers into the present. If that were possible cucumber prices would be equal in the present and the future, and the cucumber own rate would be equal to all other own rates at zero. But the point is that if any lending takes place, it will be at a zero own rate.

Second, the positive own rate on tomatoes means that there is an incentive to lend in terms of tomatoes rather than lend in terms of other commodities. But as long as it is possible to borrow in terms of other commodities at a zero own rate, no one borrows in terms of tomatoes. Thus, if anyone wanted to lend in terms of tomatoes, he would have to reduce the rate on tomatoes to make borrowers indifferent between borrowing in terms of tomatoes and borrowing in terms of some other commodity. However, if tomatoes today can be held at zero cost to be sold at the higher price prevailing next period, currently produced tomatoes would be sold in the next period rather than sold today. So if there were no costs of holding tomatoes until the next period, the price of tomatoes in the next period would be no higher than the price in the current period. In other words, the forward price of tomatoes cannot exceed the current spot price by more than the cost of holding tomatoes until the next period. If the difference between the spot and the forward price reflects no more than the cost of holding tomatoes till the next period, then, as Keynes showed in chapter 17 of the General Theory, the own rates are indeed effectively equalized after appropriate adjustment for storage costs and expected appreciation.

Thus, it was Keynes, who having selected Sraffa to review Hayek’s Prices and Production in the Economic Journal, of which Keynes was then the editor, adapted Sraffa’s own rate analysis in the General Theory, but did so in a fashion that, at least partially, rehabilitated the very natural-rate analysis that had been the object of Sraffa’s scorn in his review of Prices and Production. Keynes also rejected the natural-rate analysis, but he did so not because it is nonsensical, but because the natural rate is not independent of the level of employment. Keynes’s argument that the natural rate depends on the level of employment seems to me to be inconsistent with the idea that the IS curve is downward sloping. But I will have to think about that a bit and reread the relevant passage in the General Theory and perhaps revisit the point in a future post.

 UPDATE (07/28/14 13:02 EDT): Thanks to my commenters for pointing out that my own thinking about the own rate of interest was not quite right. I should have defined the own rate in terms of a real numeraire instead of $, which was a bit of awkwardness that I should have fixed before posting. I will try to publish a corrected version of this post later today or tomorrow. Sorry for posting without sufficient review and revision.

UPDATE (08/04/14 11:38 EDT): I hope to post the long-delayed sequel to this post later today. A number of personal issues took precedence over posting, but I also found it difficult to get clear on several minor points, which I hope that I have now resolved adequately, for example I found that defining the own rate in terms of a real numeraire was not really the source of my problem with this post, though it was a useful exercise to work through. Anyway, stay tuned.

A New Version of my Paper (with Paul Zimmerman) on the Hayek-Sraffa Debate Is Available on SSRN

One of the good things about having a blog (which I launched July 5, 2011) is that I get comments about what I am writing about from a lot of people that I don’t know. One of my most popular posts – it’s about the sixteenth most visited — was one I wrote, just a couple of months after starting the blog, about the Hayek-Sraffa debate on the natural rate of interest. Unlike many popular posts, to which visitors are initially drawn from very popular blogs that linked to those posts, but don’t continue to drawing a lot of visitors, this post initially had only modest popularity, but still keeps on drawing visitors.

That post also led to a collaboration between me and my FTC colleague Paul Zimmerman on a paper “The Sraffa-Hayek Debate on the Natural Rate of Interest” which I presented two years ago at the History of Economics Society conference. We have now finished our revisions of the version we wrote for the conference, and I have just posted the new version on SSRN and will be submitting it for publication later this week.

Here’s the abstract posted on the SSRN site:

Hayek’s Prices and Production, based on his hugely successful lectures at LSE in 1931, was the first English presentation of Austrian business-cycle theory, and established Hayek as a leading business-cycle theorist. Sraffa’s 1932 review of Prices and Production seems to have been instrumental in turning opinion against Hayek and the Austrian theory. A key element of Sraffa’s attack was that Hayek’s idea of a natural rate of interest, reflecting underlying real relationships, undisturbed by monetary factors, was, even from Hayek’s own perspective, incoherent, because, without money, there is a multiplicity of own rates, none of which can be uniquely identified as the natural rate of interest. Although Hayek’s response failed to counter Sraffa’s argument, Ludwig Lachmann later observed that Keynes’s treatment of own rates in Chapter 17 of the General Theory (itself a generalization of Fisher’s (1896) distinction between the real and nominal rates of interest) undercut Sraffa’s criticism. Own rates, Keynes showed, cannot deviate from each other by more than expected price appreciation plus the cost of storage and the commodity service flow, so that anticipated asset yields are equalized in intertemporal equilibrium. Thus, on Keynes’s analysis in the General Theory, the natural rate of interest is indeed well-defined. However, Keynes’s revision of Sraffa’s own-rate analysis provides only a partial rehabilitation of Hayek’s natural rate. There being no unique price level or rate of inflation in a barter system, no unique money natural rate of interest can be specified. Hayek implicitly was reasoning in terms of a constant nominal value of GDP, but barter relationships cannot identify any path for nominal GDP, let alone a constant one, as uniquely compatible with intertemporal equilibrium.

Aside from clarifying the conceptual basis of the natural-rate analysis and its relationship to Sraffa’s own-rate analysis, the paper also highlights the connection (usually overlooked but mentioned by Harald Hagemann in his 2008 article on the own rate of interest for the International Encyclopedia of the Social Sciences) between the own-rate analysis, in either its Sraffian or Keynesian versions, and Fisher’s early distinction between the real and nominal rates of interest. The conceptual identity between Fisher’s real and nominal distinction and Keynes’s own-rate analysis in the General Theory only magnifies the mystery associated with Keynes’s attack in chapter 13 of the General Theory on Fisher’s distinction between the real and the nominal rates of interest.

I also feel that the following discussion of Hayek’s role in developing the concept of intertemporal equilibrium, though tangential to the main topic of the paper, makes an important point about how to think about intertemporal equilibrium.

Perhaps the key analytical concept developed by Hayek in his early work on monetary theory and business cycles was the idea of an intertemporal equilibrium. Before Hayek, the idea of equilibrium had been reserved for a static, unchanging, state in which economic agents continue doing what they have been doing. Equilibrium is the end state in which all adjustments to a set of initial conditions have been fully worked out. Hayek attempted to generalize this narrow equilibrium concept to make it applicable to the study of economic fluctuations – business cycles – in which he was engaged. Hayek chose to formulate a generalized equilibrium concept. He did not do so, as many have done, by simply adding a steady-state rate of growth to factor supplies and technology. Nor did Hayek define equilibrium in terms of any objective or measurable magnitudes. Rather, Hayek defined equilibrium as the mutual consistency of the independent plans of individual economic agents.

The potential consistency of such plans may be conceived of even if economic magnitudes do not remain constant or grow at a constant rate. Even if the magnitudes fluctuate, equilibrium is conceivable if the fluctuations are correctly foreseen. Correct foresight is not the same as perfect foresight. Perfect foresight is necessarily correct; correct foresight is only contingently correct. All that is necessary for equilibrium is that fluctuations (as reflected in future prices) be foreseen. It is not even necessary, as Hayek (1937) pointed out, that future price changes be foreseen correctly, provided that individual agents agree in their anticipations of future prices. If all agents agree in their expectations of future prices, then the individual plans formulated on the basis of those anticipations are, at least momentarily, equilibrium plans, conditional on the realization of those expectations, because the realization of those expectations would allow the plans formulated on the basis of those expectations to be executed without need for revision. What is required for intertemporal equilibrium is therefore a contingently correct anticipation by future agents of future prices, a contingent anticipation not the result of perfect foresight, but of contingently, even fortuitously, correct foresight. The seminal statement of this concept was given by Hayek in his classic 1937 paper, and the idea was restated by J. R. Hicks (1939), with no mention of Hayek, two years later in Value and Capital.

I made the following comment in a footnote to the penultimate sentence of the quotation:

By defining correct foresight as a contingent outcome rather than as an essential property of economic agents, Hayek elegantly avoided the problems that confounded Oskar Morgenstern ([1935] 1976) in his discussion of the meaning of equilibrium.

I look forward to reading your comments.

Never Reason from a Disequilibrium

One of Scott Sumner’s many contributions as a blogger has been to show over and over and over again how easy it is to lapse into fallacious economic reasoning by positing a price change and then trying to draw inferences about the results of the price change. The problem is that a price change doesn’t just happen; it is the result of some other change. There being two basic categories of changes (demand and supply) that can affect price, there are always at least two possible causes for a given price change. So, until you have specified the antecedent change responsible for the price change under consideration, you can’t work out the consequences of the price change.

In this post, I want to extend Scott’s insight in a slightly different direction, and explain how every economic analysis has to begin with a statement about the initial conditions from which the analysis starts. In particular, you need to be clear about the equilibrium position corresponding to the initial conditions from which you are starting. If you posit some change in the system, but your starting point isn’t an equilibrium, you have no way of separating out the adjustment to the change that you are imposing on the system from the change the system would be undergoing simply to reach the equilibrium toward which it is already moving, or, even worse, from the change the system would be undergoing if its movement is not toward equilibrium.

Every theoretical analysis in economics properly imposes a ceteris paribus condition. Unfortunately, the ubiquitous ceteris paribus condition comes dangerously close to rendering economic theory irrefutable, except perhaps in a statistical sense, because empirical refutations of the theory can always be attributed to changes, abstracted from only in the theory, but not in the real world of our experience. An empirical model with a sufficient number of data points may be able to control for the changes in conditions that the theory holds constant, but the underlying theory is a comparison of equilibrium states (comparative statics), and it is quite a stretch to assume that the effects of perpetual disequilibrium can be treated as nothing but white noise. Austrians are right to be skeptical of econometric analysis; so was Keynes, for that matter. But skepticism need not imply nihilism.

Let me try to illustrate this principle by applying it to the Keynesian analysis of involuntary unemployment. In the General Theory Keynes argued that if adequate demand is deficient, the likely result is an equilibrium with involuntary unemployment. The “classical” argument that Keynes disputed was that, in principle at least, involuntary unemployment could not persist, because unemployed workers, if only they would accept reduced money wages, would eventually find employment. Keynes denied that involuntary unemployment could not persist, arguing that if workers did accept reduced money wages, the wage reductions would not get translated into reduced real wages. Instead, falling nominal wages would induce employers to cut prices by roughly the same percentage as the reduction in nominal wages, leaving real wages more or less unchanged, thereby nullifying the effectiveness of nominal-wage cuts, and, instead, fueling a vicious downward spiral of prices and wages.

In making this argument, Keynes didn’t dispute the neoclassical proposition that, with a given capital stock, the marginal product of labor declines as employment increases, implying that real wages have to fall for employment to be increased. His argument was about the nature of the labor-supply curve, labor supply, in Keynes’s view, being a function of both the real and the nominal wage, not, as in the neoclassical theory, only the real wage. Under Keynes’s “neoclassical” analysis, the problem with nominal-wage cuts is that they don’t do the job, because they lead to corresponding price cuts. The only way to reduce unemployment, Keynes insisted, is to raise the price level. With nominal wages constant, an increased price level would achieve the real-wage cut necessary for employment to be increased. And this is precisely how Keynes defined involuntary unemployment: the willingness of workers to increase the amount of labor actually supplied in response to a price level increase that reduces their real wage.

Interestingly, in trying to explain why nominal-wage cuts would fail to increase employment, Keynes suggested that the redistribution of income from workers to entrepreneurs associated with reduced nominal wages would tend to reduce consumption, thereby reducing, not increasing, employment. But if that is so, how is it that a reduced real wage, achieved via inflation, would increase employment? Why would the distributional effect of a reduced nominal, but unchanged real, wage be more adverse to employment han a reduced real wage, achieved, with a fixed nominal wage, by way of a price-level increase?

Keynes’s explanation for all this is confused. In chapter 19, where he makes the argument that money-wage cuts can’t eliminate involuntary unemployment, he presents a variety of reasons why nominal-wage cuts are ineffective, and it is usually not clear at what level of theoretical abstraction he is operating, and whether he is arguing that nominal-wage cuts would not work even in principle, or that, although nominal-wage cuts might succeed in theory, they would inevitably fail in practice. Even more puzzling, It is not clear whether he thinks that real wages have to fall to achieve full employment or that full employment could be restored by an increase in aggregate demand with no reduction in real wages. In particular, because Keynes doesn’t start his analysis from a full-employment equilibrium, and doesn’t specify the shock that moves the economy off its equilibrium position, we can only guess whether Keynes is talking about a shock that had reduced labor productivity or (more likely) a shock to entrepreneurial expectations (animal spirits) that has no direct effect on labor productivity.

There was a rhetorical payoff for Keynes in maintaining that ambiguity, because he wanted to present a “general theory” in which full employment is a special case. Keynes therefore emphasized that the labor market is not self-equilibrating by way of nominal-wage adjustments. That was a perfectly fine and useful insight: when the entire system is out of kilter; there is no guarantee that just letting the free market set prices will bring everything back into place. The theory of price adjustment is fundamentally a partial-equilibrium theory that isolates the disequiibrium of a single market, with all other markets in (approximate) equilibrium. There is no necessary connection between the adjustment process in a partial-equilibrium setting and the adjustment process in a full-equilibrium setting. The stability of a single market in disequilibrium does not imply the stability of the entire system of markets in disequilibrium. Keynes might have presented his “general theory” as a theory of disequilibrium, but he preferred (perhaps because he had no other tools to work with) to spell out his theory in terms of familiar equilibrium concepts: savings equaling investment and income equaling expenditure, leaving it ambiguous whether the failure to reach a full-employment equilibrium is caused by a real wage that is too high or an interest rate that is too high. Axel Leijonhufvud highlights the distinction between a disequilibrium in the real wage and a disequilibrium in the interest rate in an important essay “The Wicksell Connection” included in his book Information and Coordination.

Because Keynes did not commit himself on whether a reduction in the real wage is necessary for equilibrium to be restored, it is hard to assess his argument about whether, by accepting reduced money wages, workers could in fact reduce their real wages sufficiently to bring about full employment. Keynes’s argument that money-wage cuts accepted by workers would be undone by corresponding price cuts reflecting reduced production costs is hardly compelling. If the current level of money wages is too high for firms to produce profitably, it is not obvious why the reduced money wages paid by entrepreneurs would be entirely dissipated by price reductions, with none of the cost decline being reflected in increased profit margins. If wage cuts do increase profit margins, that would encourage entrepreneurs to increase output, potentially triggering an expansionary multiplier process. In other words, if the source of disequilibrium is that the real wage is too high, the real wage depending on both the nominal wage and price level, what is the basis for concluding that a reduction in the nominal wage would cause a change in the price level sufficient to keep the real wage at a disequilibrium level? Is it not more likely that the price level would fall no more than required to bring the real wage back to the equilibrium level consistent with full employment? The question is not meant as an expression of policy preference; it is a question about the logic of Keynes’s analysis.

Interestingly, present-day opponents of monetary stimulus (for whom “Keynesian” is a term of extreme derision) like to make a sort of Keynesian argument. Monetary stimulus, by raising the price level, reduces the real wage. That means that monetary stimulus is bad, as it is harmful to workers, whose interests, we all know, is the highest priority – except perhaps the interests of rentiers living off the interest generated by their bond portfolios — of many opponents of monetary stimulus. Once again, the logic is less than compelling. Keynes believed that an increase in the price level could reduce the real wage, a reduction that, at least potentially, might be necessary for the restoration of full employment.

But here is my question: why would an increase in the price level reduce the real wage rather than raise money wages along with the price level. To answer that question, you need to have some idea of whether the current level of real wages is above or below the equilibrium level. If unemployment is high, there is at least some reason to think that the equilibrium real wage is less than the current level, which is why an increase in the price level would be expected to cause the real wage to fall, i.e., to move the actual real wage in the direction of equilibrium. But if the current real wage is about equal to, or even below, the equilibrium level, then why would one think that an increase in the price level would not also cause money wages to rise correspondingly? It seems more plausible that, in the absence of a good reason to think otherwise, that inflation would cause real wages to fall only if real wages are above their equilibrium level.

Hawtrey v. Keynes on the General Theory and the Rate of Interest

Almost a year ago, I wrote a post briefly discussing Hawtrey’s 1936 review of the General Theory, originally circulated as a memorandum to Hawtrey’s Treasury colleagues, but included a year later in a volume of Hawtrey’s essays Capital and Employment. My post covered only the initial part of Hawtrey’s review criticizing Keynes’s argument that the rate of interest is a payment for the sacrifice of liquidity, not a reward for postponing consumption – the liquidity-preference theory of the rate of interest. After briefly quoting from Hawtrey’s criticism of Keynes, the post veered off in another direction, discussing the common view of Keynes and Hawtrey that an economy might suffer from high unemployment because the prevailing interest rate might be too high. In the General Theory Keynes theorized that the reason that the interest rate was too high to allow full employment might be that liquidity preference was so intense that the interest rate could not fall below a certain floor (liquidity trap). Hawtrey also believe that unemployment might result from an interest rate that was too high, but Hawtrey maintained that the most likely reason for such a situation was that the monetary authority was committed to an exchange-rate peg that, absent international cooperation, required an interest higher than the rate consistent with full employment. In this post I want to come back and look more closely at Hawtrey’s review of the General Theory and also at Keynes’s response to Hawtrey in a 1937 paper (“Alternative Theories of the Rate of Interest”) and at Hawtrey’s rejoinder to that response.

Keynes’s argument for his liquidity-preference theory of interest was a strange one. It had two parts. First, in contrast to the old orthodox theory, the saving-investment equilibrium is achieved by variations of income, not by variations in the rate of interest. Second – and this is where the strangeness really comes in — the rate of interest has an essential nature or meaning. That essential meaning, according to Keynes, is not a rate of exchange between cash in the present and cash in the future, but the sacrifice of liquidity accepted by a lender in forgoing money in the present in exchange for money in the future. For Keynes the existence of a margin between the liquidity of cash and the rate of interest is the essence of what interest is all about. Although Hawtrey thought that the idea of liquidity preference was an important contribution to monetary theory, he rejected the idea that liquidity preference is the essence of interest. Instead, he viewed liquidity preference as an independent constraint that might prevent the interest rate, determined, in part, by other forces, from falling to a level as low as it might otherwise.

Let’s have a look at Keynes’s argument that liquidity preference is what determines the rate of interest. Keynes begins Chapter 7 of the General Theory with the following statement:

In the previous chapter saving and investment have been so defined that they are necessarily equal in amount, being, for the community as a whole, merely different aspect of the same thing.

Because savings and investment (in the aggregate) are merely different names for the same thing, both equaling the unconsumed portion of total income, Keynes argued that any theory of interest — in particular what Keynes called the classical or orthodox theory of interest — in which the rate of interest is that rate at which savings and investment are equal is futile and circular. How can the rate of interest be said to equilibrate savings and investment, when savings and investment are necessarily equal? The function of the rate of interest, Keynes concluded, must be determined by something other than equilibrating savings and investment.

To find what it is that the rate of interest is equilibrating, Keynes undertook a brilliant analysis of own rates of interest in chapter 13 of the General Theory. Corresponding to every commodity or asset that can be held into the future, there is an own rate of interest which corresponds to the rate at which a unit of the asset can be exchanged today for a unit in the future. The money rate of interest is simply the own rate of interest in terms of money. In equilibrium, the expected net rate of return, including the service flow or the physical yield of the asset, storage costs, and expected appreciation or depreciation, must be equalized. Keynes believed that money, because it provides liquidity services, must be associated with a liquidity premium, and that this liquidity premium implied that the rate of return from holding money (exclusive of its liquidity services) had to be correspondingly less than the expected net rate of return on holding other assets. For some reason, Keynes concluded that it was the liquidity premium that explained why the own rate of interest on real assets had to be positive. The rate of interest, Keynes asserted, was not the reward for foregoing consumption, i.e., carrying an asset forward from the current period to the next period; it is the reward for foregoing liquidity. But that is clearly false. The liquidity premium explains why there is a difference between the rate of return from holding a real asset that provides no liquidity services and the rate of return from holding money. It does not explain what the equilibrium expected net rate of return from holding any asset is what it is. Somehow Keynes missed that obvious distinction.

Equally as puzzling is that Keynes also argued that there is an economic mechanism operating to ensure the equality of savings and investment, just as there is an economic mechanism (namely price adjustment) operating to ensure the equality of aggregate purchases and sales. Just as price adjusts to equilibrate purchases and sales, income adjusts to equilibrate savings and investment.

Keynes argued himself into a corner, and in his review of the General Theory, Hawtrey caught him there and pummeled him.

The identity of saving and investment may be compared to the identity of two sides of an account.

Identity so established does not prove anything. The idea that a tendency for saving and investment so defined to become different has to be counteracted by an expansion or contraction of the total of incomes is an absurdity; such a tendency cannot strain the economic system; it can only strain Keynes’s vocabulary.

Thus, Keynes’s premise that it is income, not the rate of interest, which equilibrates saving and investment was based on a logical misconception. Now to be sure, Keynes was correct in pointing out that variations in income also affect saving and investment. But that just means that income, savings, investment, the demand for money and the supply of money and the rate of interest are simultaneously determined in a macroeconomic model, a model that cannot be partitioned in such a way investment and saving depend exclusively on income and are completely independent of the rate of interest. Whatever the shortcomings of the Hicksian IS-LM model, it at least recognized that the variables in the model are simultaneously, not sequentially, determined. That Keynes, who was a highly competent and skilled mathematician, author of one of the most important works ever written on probability theory, seems to have been oblivious to this simple distinction is hugely perplexing.

In 1937, a year after publishing the General Theory, Keynes wrote an article “Alternative Theories of the Rate of Interest” in which he defended his liquidity-preference theory of interest against the alternative theories of interest of Ohlin, Robertson, and Hawtrey in which the rate of interest was conceived as the price of credit. Responding to Hawtrey’s criticism of his attempt to define aggregate investment and aggregate savings as different aspects of the same thing while also using their equality as an equilibrium condition that determines what the equilibrium level of income is, Keynes returned again to a comparison between the identity of investment and savings and the identity of purchases and sales:

Aggregate saving and aggregate investment . . . are necessarily equal in the same way in which the aggregate purchases of anything on the market are equal to the aggregate sales. But this does not mean that “buying” and “selling” are identical terms, and that the laws of supply and demand are meaningless.

Keynes went on to explain the relationship between his view that saving and investment are equilibrated by income and his view of what determines the rate of interest.

[T]he . . . novelty lies in my maintaining that it is not the rate of interest, but the level of incomes which ensures equality between saving and investment. The arguments which lead up to this initial conclusion are independent of my subsequent theory of the rate of interest, and in fact I reached it before I had reached the latter theory. But the result of it was to leave the rate of interest in the air. If the rate of interest in not determined by saving and investment in the same way in which price is determined by supply and demand, how is it determined? One naturally began by supposing that the rate of interest must be determined in some sense by productivity – that it was, perhaps, simply the monetary equivalent of the marginal efficiency of capital, the latter being independently fixed by physical and technical considerations in conjunction with expected demand. It was only when this line of approach led repeatedly to what seemed to be circular reasoning, that I hit on what I now think to be the true explanation. The resulting theory, whether right or wrong, is exceedingly simply – namely, that the rate of interest on a loan of given quality and maturity has to be established at the level which, in the opinion of those who have the opportunity of choice – i.e., of wealth-holders – equalises the attractions of holding idle cash and of holding the loan. It would be true to say that this by itself does not carry us very far. But it gives us firm and intelligible ground from which to proceed.

The concluding sentence seems to convey some intuition on Keynes’s part of how inadequate his liquidity-preference theory is as a theory of the rate of interest. But if he had thought the matter through to the bottom, he could not have claimed even that much for it.

Here is Hawtrey’s response to Keynes’s attempt to defend his position.

The part of Mr. Keynes’ article . . . which refers to my book Capital and Employment is concerned mainly with questions of terminology. He finds fault with my statement that he has defined saving and investment as “two different names for the same thing.” He himself describes them as being “for the community as a whole, merely different aspects of the same thing ” . . . . If, as I suppose, we both mean the same thing by the same thing, the distinction is rather a fine one. In Capital and Employment . . . I point out that the identity of . . . saving and investment . . . “is not a purely verbal proposition: it is an arithmetical identity, comparable to two sides of an account.”

Something very like that seems to be in Mr. Keynes’ mind when he compares the relation between saving and investment to that between purchases and sales. Purchases and sales are necessarily equal, but “this does not mean that buying and selling are identical terms, and that the laws of supply and demand are meaningless.”

Purchases and sales are also “different aspects of the same thing.” And surely, if demand were defined to mean purchases and supply to mean sales, any proposition about economic forces tending to make demand and supply equal, or about their equality being a condition of equilibrium, or indeed a condition of anything whatever, would be nonsense.

“The theory of the rate of interest which prevailed before 1914,” Mr. Keynes writes, “regarded it as the factor which ensured equality between saving and investment,” and he claims therefore that, “in maintaining the equality of saving and investment,” he is “returning to old-fashioned orthodoxy.” That is not so. Old-fashioned orthodoxy never held that saving and investment could not be unequal; it held that their inequality, when it did occur, was inconsistent with equilibrium. If they are defined as “different aspects of the same thing,” how can it possibly be “the level of incomes which ensures equality between saving and investment”? Whatever the level of incomes may be, and however great the disequilibrium, the condition that saving and investment must be equal is always identically satisfied.

While it is widely recognized that Hawtrey showed that Keynes’s attempt to define investment and savings as different aspects of the same thing and as a condition of equilibrium was untenable (a criticism made by others like Haberler and Robertson as well), the fallacy committed by Keynes was not a fatal one, though the fallacy has not been entirely extirpated from textbook expositions of the basic Keynesian model. Unfortunately, the related fallacy underlying Keynes’s attempt to transform his liquidity-preference theory of the demand for money into a full-fledged theory of the rate of interest was not as easily exposed. In his review, Hawtrey discussed various limitations of Keynes’s own-rate analysis, but, unless I have missed it, he failed to see the fallacy in supposing that liquidity premium on money explains the equilibrium net return from holding assets, which is what the real (or natural) rate of interest corresponds to in the analytical framework of chapter 13 of the General Theory.


About Me

David Glasner
Washington, DC

I am an economist at the Federal Trade Commission. Nothing that you read on this blog necessarily reflects the views of the FTC or the individual commissioners. Although I work at the FTC as an antitrust economist, most of my research and writing has been on monetary economics and policy and the history of monetary theory. In my book Free Banking and Monetary Reform, I argued for a non-Monetarist non-Keynesian approach to monetary policy, based on a theory of a competitive supply of money. Over the years, I have become increasingly impressed by the similarities between my approach and that of R. G. Hawtrey and hope to bring Hawtrey's unduly neglected contributions to the attention of a wider audience.

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