Inflation and Policy Rules

长期以来，价格水平和通货膨胀的确定一直是宏观经济学家关注的中心问题。这反映了人们普遍认为控制通货膨胀对经济福利很重要。鉴于其中心重要性，价格水平和通货膨胀的基本决定因素继续受到争议也许是令人惊讶的。最近，随着“价格水平的财政理论”的出现，这场争论变得更加激烈，这给辩论带来了新的转折。传统的货币主义观点强调了独立央行的重要性，并认为高通货膨胀最终只能由高货币增长率推动。在这种观点中，财政政策是重要的，但主要是因为过度的赤字可能最终迫使央行货币化。根据财政理论，政府可以只使用财政变量直接瞄准价格水平，比如未来盈余的现值和名义债务的当前水平。这两种观点源于不同研究者在均衡概念上的重要差异。调和这些差异的失败源于这样一个事实，即经济的一个关键特征——价格形成机制——是隐性的。这个项目使用博弈论来充分说明价格是如何从经济中的政府和私人参与者的行为中产生的，而不是诉诸于瓦尔拉斯拍卖师的虚构。在这种环境下，政府显然不可能事先承诺一系列独立于私人部门行动的基本盈余/赤字，除非在非常特殊的情况下。然而，这种对价格水平财政理论关键假设的否定结论并没有延伸到其关键结果：价格水平仍然可以由财政政策来确定。当货币被明确建模时，将通货膨胀与高货币增长率联系起来的传统结果就恢复了；然而，即使在利率挂钩的情况下，财政理论也会导致一种独特的均衡，而这种均衡以前通常与价格不确定性联系在一起。完整地阐明导致价格水平财政理论的政府战略假设对于政策建议是非常重要的。先前关于这一主题的论文声称，价格稳定可以通过政府坚定地承诺忽视任何债务危机，并奉行外生和固定盈余/赤字政策来实现。这个项目表明，在债务危机中，政府被迫进行财政调整。通过经济的财政方面实现价格确定性的适当建议是，在危机期间增加税收，而不减税。这样的策略会使债务危机的预期弄巧成拙，但承诺的能力和这种承诺的可信度可能比之前论文所倡导的政策规则所需要的问题要大得多。从理论的角度来看，这里开发的方法对于更广泛的问题是有价值的。该项目表明，在政策规则的描述（规定了政府在所有突发事件下应如何反应）和宏观经济学中使用的竞争均衡的定义（仅描述均衡分配和价格）之间存在根本的紧张关系。因此，对经济的博弈论描述可以帮助我们重新审视大量研究采用特定政策规则如何避免或导致均衡不确定性的文献。

The determination of the price level and inflation has long been a central concern for macroeconomists. This reflects the widespread view that the control of inflation is important for economic welfare. In view of its central importance, it is perhaps surprising that the basic determinants of the price level and inflation continue to be under dispute. Recently, this dispute has become more heated with the arrival of the "fiscal theory of the price level" which puts a new twist on the debate. The traditional, monetarist view has highlighted the importance of an independent central bank and has held that high inflation can only be ultimately fueled by high rates of money growth. In this view, the fiscal policy is important, but mainly so because excessive deficits may eventually force the central bank to monetize. According to the fiscal theory, the government can instead target directly the price level using fiscal variables alone, such as the present value of future surpluses and the current level of nominal debt.These two views stem from important differences in the equilibrium concept different researchers have in mind. The failure to reconcile these differences follows from the fact that a key feature of the economy, the price-formation mechanism, is left implicit. This project uses game theory to fully specify how prices arise from the actions of the government and the private players in the economy, without resorting to the fiction of a Walrasian auctioneer. In this environment, it is plainly impossible for the government to commit in advance to a sequence of primary surpluses/deficits that is independent of the actions of the private sector, except in a very special case. However, this negative conclusion on the key assumption of the fiscal theory of the price level does not extend to its key result: the price level can still be pinned down by the fiscal policy. When money is explicitly modeled, the traditional result linking inflation to high money growth rates is restored; however, the fiscal theory leads to a unique equilibrium even with an interest rate peg, which was previously commonly associated with price indeterminacy.Spelling out completely the assumptions on the government strategy that lead to a fiscal theory of the price level is very important for policy advice. Previous papers on the subject claimed that price stability could be achieved by a firm commitment by the government to ignore any debt crisis and pursue a policy of exogenous and fixed surpluses/deficits. This project shows that in a debt crisis a fiscal adjustment is forced onto the government. The appropriate advice for achieving price determinacy through the fiscal side of the economy calls for more taxes during the crisis without any tax cut ever. Such a strategy would make the expectations of a debt crisis self-defeating, but both the ability to commit to it and the credibility of such a commitment might be much more problematic than what is needed for the policy rule advocated by previous papers.From a theoretical perspective, the approach developed here is valuable for a wider class of problems. This project shows that there is a fundamental tension between the description of a policy rule, which specifies how the government should react under all contingencies, and the definition of a competitive equilibrium used in macroeconomics, that only describes equilibrium allocations and prices. A game-theoretic description of the economy can thus be useful to revisit the vast literature that studies how the adoption of a particular policy rule can avoid or cause equilibrium indeterminacy.