آینده حجم پول در تجزیه و تحلیل سیاست های پولی

This paper considers the role of monetary aggregates in modern macroeconomic models of the New Keynesian type. The focus is on future model developments that are suggested by the monetarist literature, and that in addition seem justified empirically. Both the relation between money and inflation, and between money and aggregate demand, are considered. Regarding the first relation, it is argued that both the mean and the dynamics of inflation in present-day models are governed by money growth. This arises from a conventional aggregate-demand channel; claims that an emphasis on the link between monetary aggregates and inflation requires a direct channel connecting money to inflation, are wide of the mark. The relevance of money for aggregate demand, in turn, comes not via real balance effects (or other justifications for money in the IS equation), but on money serving as a proxy for the various substitution effects of monetary policy that exist when many asset prices matter for aggregate demand. This role for monetary aggregates is supported by empirical evidence and enhances the value of money to monetary policy.

The paper by Taylor (1993) was pivotal in shaping the conduct of monetary policy analysis. Monetary economists had long recognized that central banks in practice treated the nominal interest rate rather than the monetary base or a reserves aggregate as their policy instrument. They had also acknowledged that interest-rate rules that responded to nominal variables in an appropriate manner could deliver low and stable inflation, even if these rules did not respond directly to movements in the money stock.1 But Taylor put these elements together with an empirical insight, namely, that actual monetary policy decisions could be usefully approximated by a simple interest-rate rule that responded to observed movements in a small set of key variables—inflation and detrended output. Taylor's insight has facilitated the use of small-scale models that analyze monetary policy, the business cycle, and inflation with interest-rate rules (see e.g. the papers in Taylor, 1999). In itself, the use of a Taylor rule for monetary policy analysis is neutral on the issue of the importance of monetary aggregates. The fact that actual policy is well characterized by a rule with no explicit money term does not preclude a role for monetary aggregates in the transmission of monetary policy or the analysis of inflation. Nevertheless, the literature that has found the Taylor rule a useful way of characterizing monetary policy has also endorsed the use of New Keynesian models that feature no explicit reference to monetary aggregates (e.g. Clarida et al., 1999, pp. 1686–1687; Rotemberg and Woodford, 1997, p. 309).2 It is not difficult to see why this development has taken place: if policy actions can be characterized in terms of movements in interest rates, it is convenient to trace the transmission of policy effects through the reaction of aggregate demand to interest rates. Moreover, some analysts who reject Taylor rules as a useful description of actual monetary policy behavior have nevertheless supported the movement away from the use of monetary aggregates in monetary policy analysis (e.g. Svensson, 2003). This paper aims to answer four questions about the future of monetary aggregates in monetary policy analysis, two on the relationship between money and inflation, and two on the transmission mechanism of monetary policy. The questions are: (a) Do the new Keynesian models referred to above imply that inflation in the long run is governed by money growth, as stressed by the quantity theory of money? (b) Can inflation dynamics in these models be given a conventional quantity-theory interpretation? (c) Is the basic transmission mechanism of monetary policy in these models the same as that in pre-1990s models, which apparently gave a more explicit role to money? (d) Finally, are there aspects of the transmission mechanism of monetary policy present in the pre-1990s work that could usefully be added to new Keynesian models? Throughout, my investigation of these questions will be with the aim of determining whether the behavior of monetary aggregates deserves attention in the decision-making of inflation-targeting central banks that use an interest-rate operating instrument. At a conference in July 1992, Taylor made his own position clear. While observing that “interest rates are likely to remain the preferred operating instrument of monetary policy”, Taylor (1992, p. 12) advised: “The evidence that the large swings in inflation are related to money growth indicates, however, that money should continue to play an important role in monetary policy formulation in the future.” The subsequent decade of monetary policy formulation, however, has seen a move away from this prescription, with continuing de-emphasis of money on the part of the Federal Reserve and other central banks, and with the European Central Bank's assignment of a prominent role to money being the basis for sharp criticism from a number of economists (e.g. Begg et al., 2002; Galı́, 2002; Rudebusch and Svensson, 2002; Svensson 1999a (1999a), Svensson 1999a (1999b) and Svensson 1999a (2002)). Such criticism, on the surface, appears to be justified by current models for monetary policy—which, a variety of observers claim (see Section 2 below), give money much-diminished importance compared to its role in the quantity theory. In answering the above questions, I make two departures from much recent work on money. First, while money demand behavior is an important element of my discussion, I do not focus on the issue of formal stability of the money demand function. One reason for this is that, as stressed by Rudebusch and Svensson (2002), a stable money demand function does not preclude the optimality of monetary policy arrangements which proceed without any reliance on data on the money stock. Another reason, noted by Lucas (1980), is that numerical stability of money demand neither implies nor is implied by a close relationship between money growth and inflation. A further reason is that observed instability of empirical money demand functions may reflect omission of important determinants of money demand; but the dependence of money on these determinants gives it an indicator role that may be a reason for continuing to monitor money. This last reason leads me into the second major departure from other recent approaches to the role of money. Much of this work has highlighted novel properties of models that include a term involving money, either in the policy rule or in the structural equations. For example, Christiano and Rostagno (2001) show how a strategy that includes a monitoring range for money growth serves as an insurance policy against undesirable multiple equilibria. Other studies have evaluated the size of cross-derivative terms involving money in households’ utility functions (Andrés et al., 2001; Ireland, 200la; McCallum, 2000; Woodford, 2003). My approach is different. I endeavor to determine whether money in current models has the role advanced for it in the work of Milton Friedman, Anna Schwartz, Karl Brunner, and Allan Meltzer. It was, after all, largely the work of these authors that was the basis for the “monetarist counter-revolution” (Friedman, 1970) in the 1960s that changed macroeconomists’ views regarding the potency of monetary policy and the importance of monetary aggregates.3 Focusing on their work helps identify the distinguishing features of current models for monetary policy.4 Various combinations of answers to the above questions are possible. One is that current models represent a decisive rejection of the earlier quantity-theory-based analysis, but that this rejection is theoretically and empirically justified. In that case, the answers to (a)–(d) above are all “no”, and, insofar as there is a role for money in monetary analysis, it must be based on a new justification different from those advanced by monetarists. Another answer is that the differences between current models and their monetarist antecedents are more apparent than real, and so an eclectic interpretation of current models indicates that they have standard monetarist properties. Then questions (a)–(c) should be answered with “yes”, and (d), “no.”5 The conclusion suggested by the analysis in this paper, however, is that while current models are partially monetarist, further insights from monetarist analysis could be fruitfully added to New Keynesian models. I argue in Section 2 that present models are consistent with quantity-theory or monetarist approaches regarding their modeling of inflation. The relation between monetary policy and aggregate demand in New Keynesian models is discussed in Section 3, and I argue that, in basic terms, the transmission mechanism is a special case of that in monetarist models. New Keynesian models lack, however, an important element of most monetarist analysis. This is the notion that a spectrum of yields matters for the determination of aggregate demand and money demand. The implication of this model feature is that money conveys information about monetary conditions not summarized by the short-term interest rate. 6 I argue that there is support for adding this model feature to New Keynesian models. In total, the analysis suggests answers of “yes” to (a)–(d) above.

The detailed conclusions of this paper are given in 2.6 and 3.4 above. Here I simply observe that for cyclical analysis the most fruitful area in which money can play a greater role is as a proxy for yields that matter for aggregate demand, some of which do not have a ready counterpart in securities-market interest rates. Associated with this is a more general specification of New Keynesian models to include, as in Friedman (1956), a spectrum of cost variables in households’ money-holding decision. This proposed modification does not overturn the legitimacy of concerns about the problems of measuring money in practice. But measurement and instability problems are not isolated to relationships involving money; the IS and Phillips curve relations also involve unobservable shock terms, and it is likely that both the shock processes and the structural parameters in these equations exhibit some nonconstancy. Nor does the contention—which the analysis above has endorsed—that money does not appear explicitly in either the Phillips curve or IS function, justify not bothering to model money. The information imparted to money by its relationship to yields that matter for aggregate demand, gives money value to monetary policy, even when money is absent from the key structural relationships