We investigate how a positive relation between inflation and capital investment (the Mundell–Tobin effect, MT-E) affects optimal monetary policy in a framework that combines overlapping generations and new Monetarist models. We find that inflation rates above the Friedman rule are optimal if and only if there is an MT-E. In the absence of the MT-E, the Friedman rule is optimal. With an MT-E, increasing inflation above the Friedman rule leads to a first-order welfare gain from increasing capital investment, and only to a second-order welfare loss from reducing consumption in markets where liquidity matters.

中文翻译：

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流动性、蒙代尔-托宾效应和弗里德曼规则

我们研究了通货膨胀和资本投资之间的正相关关系（蒙代尔-托宾效应，MT-E）如何在一个结合了重叠世代和新货币主义模型的框架中影响最优货币政策。我们发现，当且仅当存在 MT-E 时，高于弗里德曼规则的通货膨胀率才是最优的。在没有 MT-E 的情况下，弗里德曼规则是最优的。在 MT-E 中，高于弗里德曼规则的通胀率会导致增加资本投资带来的一阶福利收益，而在流动性很重要的市场中，减少消费只会导致二阶福利损失。