Economists have the least influence on policy where they know the most and are most agreed; they have the most influence on policy where they know th… - Alan Blinder

The word ‘Keynesian’ means many things to many people. Decades ago, it was a carelessly applied label for economic liberals and interventionists in general. For a while in the late 1970s and early 1980s it became a pejorative term more or less synonymous with old-fashioned.

For a period of roughly 35 years, Keynesian theory provided a central paradigm for macroeconomists, and considerable progress was made on several empirical fronts. It was widely recognized that some of the ingredients of Keynesian economics (e.g. money illusion and/or nominal wage rigidity) rested on slender to non-existent microtheoretic foundations; and there were always dissenters. But, thought of as a collection of empirical regularities that fit together into a coherent whole, the theory worked tolerably well. In the 1970s, however, the Keynesian paradigm was rejected by a great many academic economists, especially in the United States, in favour of what we now call new classical economics. By about 1980, it was hard to find an American academic macroeconomist under the age of 40 who professed to be a Keynesian. That was an astonishing intellectual turnabout in less than a decade, an intellectual revolution for sure.

The new arguments for rules take an entirely different tack. They are based neither on the ignorance nor the knavery of public officials and, in fact, assume that everyone knows how the economy operates—even the government! Moreover, the government's objectives are assumed to coincide with the people's objectives, and everyone has rational expectations. Despite these seemingly ideal circumstances, modern critics argue that a central bank left with discretion will err systematically in the direction of excessive inflation. To remedy this distortion, they advocate a fixed rule.