قوانین سیاست های پولی بهینه و کارآمد در یک مدل دنباله ای رو به جلو

This paper shows that two monetary policy strategies––hybrid nominal income targeting and strict inflation targeting––are efficient strategies of monetary policy in the sense that they are special cases of the optimal monetary policy strategy. In the case of a hybrid nominal income targeting strategy, the policymaker chooses a unitary trade-off between real output and the rate of inflation, while under strict inflation targeting the policymaker attaches a zero weight on output in the optimal policy rule.

Current discussions of issues in monetary policy share a number of characteristics. First, there has been a move toward a new framework where the rate of inflation––and not the price level––features prominently. The new approach emphasizes simplicity over complexity. It comprises a simple two-equation IS-Phillips Curve framework where real output and the rate of inflation enter as the two endogenous variables. Practical considerations have led to the omission of the LM relation from the analysis. As most central banks use a short-term nominal interest rate to set the stance of monetary policy, the inclusion of money demand in the analysis will merely serve to determine the volume of the money supply that is consistent with the set interest rate.1 Despite the adoption of an alternative framework for the analysis of monetary policy issues, there remains some disagreement among economists about the proper specification of the underlying structural relations. Of the competing specifications, two have attracted particular attention. One approach assumes that real output and the rate of inflation exhibit persistence, that is, that current real output and the rate of inflation are tied to their past behavior. In the literature this specification is referred to as “backward-looking”.2 In sharp contrast, the “forward-looking” specification adopts a rational expectations framework where current real output and the rate of inflation, respectively, depend on the next period's expected level.3 Another characteristic common to current and recent contributions to the literature is the renewed interest in the properties of monetary policy rules. In view of the widespread disagreement among economists about the proper specification of macroeconomic relationships, efforts have been made to examine the properties of simple, tractable rules across a wide variety of macroeconomic models. The idea here is to examine the robustness of candidate rules for inflation targets, price level targets, nominal income targets, exchange rate targets, and other rules such as the Taylor Rule.4 For instance, Ball (1997) finds nominal income targeting to be inconsistent with the optimal policy rule in a simple backward-looking model. Indeed he labels nominal income targeting a disastrous strategy of monetary policy as it leads to instability in both the rate of inflation and the output gap. This result is challenged by McCallum (1997) who attributes Ball's findings to the backward specification of the Phillips Curve.5 The current paper takes the forward-looking model as the baseline model to derive the optimal monetary policy rule. The paper takes the view that optimal monetary policy ought to be framed in terms of the ultimate goal variables, real output and the rate of inflation, with the relative emphasis on the two goal variables in the optimal rule determined by the underlying preferences of the policymaker and the structural parameter in the Phillips Curve. In addition, this paper shows that two simple monetary policy rules, hybrid nominal income targeting and strict inflation targeting, are special cases of the optimal monetary policy rule. The paper is organized as follows. Section 2 presents the forward-looking model. The optimal monetary policy rule is derived in Section 3. Section 4 discusses two efficient monetary policy strategies. Section 5 concludes.

This paper shows that two monetary policy strategies––hybrid nominal income targeting and strict inflation targeting––are efficient strategies in the sense that they are special cases of the optimal monetary policy strategy. Indeed, any monetary policy strategy that is centered on the ultimate goal variables––the output gap and the rate of inflation––satisfies this criterion. The critical issue is to determine the weight on real output in the optimal rule. This weight is shown to depend on the preferences of the policymaker and the structural parameter on the output gap in the Phillips Curve. With 0<θ<∞, the optimal monetary policy rule in the forward-looking model is consistent with what Svensson (1997) terms “flexible” inflation targeting in the backward-looking model.