There are four headwinds that are just hitting the American economy in the face. They're demographics, education, debt and inequality. They're powerf… - Robert J. Gordon

The century of revolution in the United States after the Civil War was economic, not political, freeing households from an unremitting daily grind of painful manual labor, household drudgery, darkness, isolation, and early death. Only one hundred years later, daily life had changed beyond recognition. Manual outdoor jobs were replaced by work in air-conditioned environments, housework was increasingly performed by electric appliances, darkness was replaced by light, and isolation was replaced not just by travel, but also by color television images bringing the world into the living room. Most important, a newborn infant could expect to live not to age forty-five, but to age seventy-two. The economic revolution of 1870 to 1970 was unique in human history, unrepeatable because so many of its achievements could happen only once.

During the relatively brief period in the late 1960s when economists were pondering the possible obsolescence of business cycles, the scholarly discipline of macroeconomics showed signs of becoming fragmented into speciality areas devoted to components of the then popular large-scale econometric models-for example, consumption, investment, money demand, and the Phillips curve. But more recently the revival of severe real world business cycles, together with the revolutions associated with Milton Friedman's monetarism and Lucas's classical equilibrium models, has brought about a revival of interest in economic analysis that focuses on a few broad aggregates summarizing activity in the economy as a whole-nominal and real income, the inflation rate, and the unemployment rate.

Part of the downfall came early and on theoretical grounds, with the realization that real-world information lags for aggregate variables like the price level and money supply were much too short to rationalize the persistent multiyear deviations from equilibrium that seemed to characterize business cycles in most industrialized countries. The second dubious assumption, continuous market clearing, was viewed more critically once it was recognized that it was not an inextricable concomitant of rational expectations, especially when Stanley Fischer (1977) and Edmund Phelps and John Taylor (1977) showed that rational expectations could be embedded in a model containing real-world institutional features like multiperiod wage and price contracts to generate nonmarket-clearing behavior. Once Fischer and Phelps-Taylor had shown that rational expectations by itself was a necessary but not a sufficient condition to validate new-classical policy conclusions, the race was on to develop the new-Keynesian theory based on rational expectations and one or another institutional impediment to continuous market clearing.