Obstfeld Maurice, Rogoff Kenneth
University of California, Berkeley, United States of America.
Harvard University, United States of America.
Rev Econ Dyn. 2021 Apr;40:1-11. doi: 10.1016/j.red.2020.08.004. Epub 2020 Sep 1.
This paper revisits the debate on ruling out speculative hyperinflations in monetary models. Although apparently a narrow issue, studying these extreme economies turns out to be quite illuminating in understanding the fundamentals of price level determination. It is also relevant in evaluating the broader claims that advocates of the fiscal theory of the price level have made. In Obstfeld and Rogoff (1983, 1986) we show that in pure fiat money models with rational expectations, where the government gives no backing whatsoever to currency, there is in fact no reasonable way to rule out speculative hyperinflations where the value of money goes to zero, even if the money supply itself is exogenous and constant. Such perverse equilibria are ruled out, however, if the government provides even a very small real backing to the currency - a fiscal mechanism, but one that comes into play only as a backstop. Indeed that backing does not have to be certain. Cochrane (2011, 2019), however, argues that this result is wrong, and that fractional currency backing is a Maginot line that is insufficient to rule out hyperinflation. We show here why, in fact, his analysis involves a subtle change in model specification that adds a distinct monetary fragility to our model. Our baseline analysis uses a canonical money-in-the-utility-function setup due to Brock (1974, 1975), but following Wallace (1981), we show the same results go through in an overlapping-generations model of money.
本文重新审视了货币模型中排除投机性恶性通货膨胀的争论。尽管这显然是一个狭义的问题，但研究这些极端的经济情况对于理解物价水平决定的基本原理却颇具启发性。这对于评估物价水平财政理论倡导者所提出的更广泛主张也具有相关性。在奥伯斯费尔德和罗戈夫（1983年、1986年）的研究中，我们表明，在纯粹的法定货币模型且具有理性预期的情况下，即政府对货币完全不提供任何支持，实际上不存在合理的方法来排除货币价值归零的投机性恶性通货膨胀，即便货币供给本身是外生且恒定的。然而，如果政府哪怕只为货币提供非常小的实际支持——一种财政机制，但仅作为后盾发挥作用，那么这种反常的均衡就会被排除。实际上，这种支持并不需要是确定无疑的。然而，科克伦（2011年、2019年）认为这一结果是错误的，并且部分货币支持是一条马其诺防线，不足以排除恶性通货膨胀。我们在此表明，实际上他的分析涉及模型设定的一个微妙变化，给我们的模型增添了一种独特的货币脆弱性。我们的基准分析采用了布罗克（1974年、1975年）提出的效用函数中货币的标准设定，但遵循华莱士（1981年）的研究，我们表明在货币的代际交叠模型中也会得出相同的结果。
