Mark Thoma had this up on Facebook. and pulled this from Tim Taylor’s Conversable Economist. It is an interesting read.

“Fifty years ago in 1968, Milton Friedman’s Presidential Address to the American Economic Association set the stage for battles in macroeconomics that have continued ever since. The legacy of the talk has been important enough that in the Winter 2018 issue of the Journal of Economic Perspectives, where I work as Managing Editor (Tim Taylor), we published a three-paper symposium on ‘Friedman’s Natural Rate Hypothesis After 50 Years.'”

What was the key insight or argument in Friedman’s 1968 address? Friedman offers a reminder that interest rates and unemployment rates are set by economic forces. Friedman uses this idea to build a distinction between the long-run and the short-run. In the short run, it is possible for a central bank like the Federal Reserve to influence interest rates and the unemployment rate. In the long run, there is a “natural” rate of interest and a “natural” rate of unemployment which is trying to emerge, gradually, over time from all the various forces in the economy.

The rest you can read for yourself at Tim’s site.