Independent Central Banks: Low Inflation at No Costs?
为Alesina和Summers（1993）的发现提供理论解释：独立中央银行能降低平均通胀且不增加产出波动，通过区分经济冲击和政策不确定性两种波动来源，说明独立性对产出波动的总体影响是模糊的。
A widely held view suggests that politically independent central banks bring about relatively low and stable inflation rates.' A more debated question is whether one has to pay for this good outcome with more real instability. In his seminal contribution, Kenneth Rogoff (1985) suggests that an independent and inflation-averse central bank reduces average inflation but, as a result, increases output variability; the conservative central banker reduces the inflation bias, due to the time-inconsistency problem, but stabilizes less. However, Alesina and Summers (1993) do not find that, at least within the OECD countries, more independent central banks are associated with more variability of growth or unemployment. Thus, they conclude that independent central banks bring about low inflation at no apparent real costs. The point of this paper is to provide theoretical underpinnings to this finding, which is in contrast to Rogoff (1985).2 The basic idea is that one can isolate two sources of output variability. One is the economic variability induced by standard exogenous shocks that monetary policy is supposed to stabilize, for instance, money demand shocks or supply shocks. The second source of variability is or, more generally, policy-induced. This is the variability introduced in the system by the uncertainty about the future course of policy. For instance, Alesina (1987) studies the effect of uncertain electoral outcomes in a model where the two contending parties have different preferences over inflation and unemployment. An inflation-averse, independent central banker does not stabilize as much the economic variability, in order to keep inflation low and stable. This is Rogoff's point. However, by insulating monetary policy from political pressures, an independent central bank can reduce the variability. The overall effect of independence on output variability is, thus, ambiguous. This result is consistent, at least prima facie, with the evidence in Alesina and Summers (1993) on the lack of correlation between centralbank independence and output variability. In fact, it is possible that when the politically induced output variability is predominant, a more independent central bank reduces average inflation and the variance of output.