Kudos to David Beckworth for eliciting a welcome concession or clarification from Paul Krugman that monetary policy is not necessarily ineffectual at the zero lower bound. The clarification is welcome because Krugman and Simon Wren Lewis seemed to be making a big deal about insisting that monetary policy at the zero lower bound is useless if it affects only the current, but not the future, money supply, and touting the discovery as if it were a point that was not already well understood.
Now it’s true that Krugman is entitled to take credit for having come up with an elegant way of showing the difference between a permanent and a temporary increase in the monetary base, but it’s a point that, WADR, was understood even before Krugman. See, for example, the discussion in chapter 5 of Jack Hirshleifer’s textbook on capital theory (published in 1970), Investment, Interest and Capital, showing that the Fisher equation follows straightforwardly in an intertemporal equilibrium model, so that the nominal interest rate can be decomposed into a real component and an expected-inflation component. If holding money is costless, then the nominal rate of interest cannot be negative, and expected deflation cannot exceed the equilibrium real rate of interest. This implies that, at the zero lower bound, the current price level cannot be raised without raising the future price level proportionately. That is all Krugman was saying in asserting that monetary policy is ineffective at the zero lower bound, even though he couched the analysis in terms of the current and future money supplies rather than in terms of the current and future price levels. But the entire argument is implicit in the Fisher equation. And contrary to Krugman, the IS-LM model (with which I am certainly willing to coexist) offers no unique insight into this proposition; it would be remarkable if it did, because the IS-LM model in essence is a static model that has to be re-engineered to be used in an intertemporal setting.
Here is how Hirshleifer concludes his discussion:
The simple two-period model of choice between dated consumptive goods and dated real liquidities has been shown to be sufficiently comprehensive as to display both the quantity theorists’ and the Keynesian theorists’ predicted results consequent upon “changes in the money supply.” The seeming contradiction is resolved by noting that one result or the other follows, or possibly some mixture of the two, depending upon the precise meaning of the phrase “changes in the quantity of money.” More exactly, the result follows from the assumption made about changes in the time-distributed endowments of money and consumption goods. pp. 150-51
Another passage from Hirshleifer is also worth quoting:
Imagine a financial “panic.” Current money is very scarce relative to future money – and so monetary interest rates are very high. The monetary authorities might then provide an increment [to the money stock] while announcing that an equal aggregate amount of money would be retired at some date thereafter. Such a change making current money relatively more plentiful (or less scarce) than before in comparison with future money, would clearly tend to reduce the monetary rate of interest. (p. 149)
In this passage Hirshleifer accurately describes the objective of Fed policy since the crisis: provide as much liquidity as needed to prevent a panic, but without even trying to generate a substantial increase in aggregate demand by increasing inflation or expected inflation. The refusal to increase aggregate demand was implicit in the Fed’s refusal to increase its inflation target.
However, I do want to make explicit a point of disagreement between me and Hirshleifer, Krugman and Beckworth. The point is more conceptual than analytical, by which I mean that although the analysis of monetary policy can formally be carried out either in terms of current and future money supplies, as Hirshleifer, Krugman and Beckworth do, or in terms of price levels, as I prefer to do so in terms of price levels. For one thing, reasoning in terms of price levels immediately puts you in the framework of the Fisher equation, while thinking in terms of current and future money supplies puts you in the framework of the quantity theory, which I always prefer to avoid.
The problem with the quantity theory framework is that it assumes that quantity of money is a policy variable over which a monetary authority can exercise effective control, a mistake — imprinted in our economic intuition by two or three centuries of quantity-theorizing, regrettably reinforced in the second-half of the twentieth century by the preposterous theoretical detour of monomaniacal Friedmanian Monetarism, as if there were no such thing as an identification problem. Thus, to analyze monetary policy by doing thought experiments that change the quantity of money is likely to mislead or confuse.
I can’t think of an effective monetary policy that was ever implemented by targeting a monetary aggregate. The optimal time path of a monetary aggregate can never be specified in advance, so that trying to target any monetary aggregate will inevitably fail, thereby undermining the credibility of the monetary authority. Effective monetary policies have instead tried to target some nominal price while allowing monetary aggregates to adjust automatically given that price. Sometimes the price being targeted has been the conversion price of money into a real asset, as was the case under the gold standard, or an exchange rate between one currency and another, as the Swiss National Bank is now doing with the franc/euro exchange rate. Monetary policies aimed at stabilizing a single price are easy to implement and can therefore be highly credible, but they are vulnerable to sudden changes with highly deflationary or inflationary implications. Nineteenth century bimetallism was an attempt to avoid or at least mitigate such risks. We now prefer inflation targeting, but we have learned (or at least we should have) from the Fed’s focus on inflation in 2008 that inflation targeting can also lead to disastrous consequences.
I emphasize the distinction between targeting monetary aggregates and targeting the price level, because David Beckworth in his post is so focused on showing 1) that the expansion of the Fed’s balance sheet under QE has been temoprary and 2) that to have been effective in raising aggregate demand at the zero lower bound, the increase in the monetary base needed to be permanent. And I say: both of the facts cited by David are implied by the fact that the Fed did not raise its inflation target or, preferably, replace its inflation target with a sufficiently high price-level target. With a higher inflation target or a suitable price-level target, the monetary base would have taken care of itself.
PS If your name is Scott Sumner, you have my permission to insert “NGDP” wherever “price level” appears in this post.