Inflation and Policy Rules

价格水平和通货膨胀的决定一直是宏观经济学家关注的中心问题。这反映了一种普遍的观点，即控制通货膨胀对经济福利很重要。鉴于其核心重要性，价格水平和通货膨胀的基本决定因素继续受到争议，这也许令人惊讶。最近，随着“物价水平财政论”的出现，这一争论又有了新的变化。传统的货币主义观点强调了独立的中央银行的重要性，并认为高通胀最终只能由高货币增长率推动。在这种观点看来，财政政策很重要，但主要是因为过度的赤字最终可能迫使央行货币化。在财政理论中，政府也可以只使用未来盈余的现值和名义债务的现状等财政变量，直接以价格水平为目标。这两种观点的根源在于，不同研究者对均衡概念的理解存在重大差异。无法调和这些差异的原因在于，经济的一个关键特征--价格形成机制--没有得到明确的解释。这个项目使用博弈论来充分说明价格是如何从政府和经济中的私人参与者的行为中产生的，而不是诉诸于瓦尔拉斯拍卖商的虚构。在这种环境下，除非在非常特殊的情况下，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。然而，对价格水平财政理论的关键假设的否定结论并没有延伸到其关键结果：价格水平仍然可以被财政政策所牵制。在明确地模拟货币时，恢复了通货膨胀与货币高增长率之间的传统关系，但是，在以往的物价不确定性中，即使是钉住利率的情况下，财政理论也会导致唯一的均衡。因此，明确地说明物价水平的财政理论所基于的政府战略的假设，对于政策建议非常重要。以前关于这个问题的论文声称，价格稳定可以通过政府坚定地承诺无视任何债务危机并奉行外生和固定盈余/赤字的政策来实现。该项目表明，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决定性的适当建议是，在危机期间征收更多的税，而永远不减税。这样的策略会使债务危机的预期弄巧成拙，但无论是承诺的能力，这种承诺的可信度可能是更大的问题比什么是所需要的政策规则由以前的文件提倡从理论的角度来看，这里开发的方法是有价值的更广泛的一类问题。该项目表明，在政策规则的描述和宏观经济学中使用的竞争性均衡的定义之间存在根本性的紧张关系，政策规则规定了政府在所有突发事件中应该如何反应，而竞争性均衡仅描述均衡分配和价格。因此，对经济的博弈论描述有助于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.