What Do We Know about Macroeconomics that Fisher and Wicksell Did Not?
回顾20世纪宏观经济学史，分为三个阶段：1940年前探索期、1940-1980年整合期（IS-LM到动态一般均衡模型）及1980年后聚焦市场不完美的新探索期，指出当前看似混乱的探索实为高产研究期。
This essay argues that the history of macroeconomics during the twentieth century can be divided into three epochs. Pre-1940: a period of exploration, during which all the right ingredients were developed. But also a period where confusion reigned, because of the lack of an integrated framework. From 1940 to 1980: a period during which an integrated framework was developed—from the <it>IS-LM</it> to dynamic general equilibrium models. But a construction with an Achilles'heel, too casual a treatment of imperfections, leading to a crisis in the late 1970s. Since 1980: a new period of exploration, focused on the role of imperfections in macroeconomics. Exploration often feels like confusion. But behind it is one of the most productive periods of research in macroeconomics.