Edmund Phelps in the context of Golden rule savings rate

The natural rate of unemployment is the name that was given to a key concept in the study of economic activity. Milton Friedman and Edmund Phelps, tackling this 'human' problem in the 1960s, both received the Nobel Memorial Prize in Economic Sciences for their work, and the development of the concept is cited as a main motivation behind the prize. A simplistic summary of the concept is: 'The natural rate of unemployment, when an economy is in a steady state of "full employment", is the proportion of the workforce who are unemployed'. Put another way, this concept clarifies that the economic term "full employment" does not mean "zero unemployment". It represents the hypothetical unemployment rate consistent with aggregate production being at the "long-run" level. This level is consistent with aggregate production in the absence of various temporary frictions such as incomplete price adjustment in labor and goods markets. The natural rate of unemployment therefore corresponds to the unemployment rate prevailing under a classical view of determination of activity.

The natural unemployment rate is mainly determined by the economy's supply side, and hence production possibilities and economic institutions. If these institutional features involve permanent mismatches in the labor market or real wage rigidities, the natural rate of unemployment may feature involuntary unemployment. The natural rate of unemployment is a combination of frictional and structural unemployment that persists in an efficient, expanding economy when labor and resource markets are in equilibrium.

The Phillips curve is a representation of the relationship between unemployment and inflation in the macroeconomy, where a tradeoff between low unemployment and price stability exists. Identified by economist Bill Phillips, the curve shows a relationship between lowering unemployment with increasing wages in an economy. While Phillips did not directly link employment and inflation, this was a trivial deduction from his statistical findings. Classical economists Paul Samuelson and Robert Solow made the connection explicit, followed by the theoretical arguments developed by Milton Friedman and Edmund Phelps.

While there is a short-run tradeoff between unemployment and inflation, it has not been observed in the long run. In 1967 and 1968, Friedman and Phelps asserted that the Phillips curve was only applicable in the short run and that, in the long run, inflationary policies would not decrease unemployment. Friedman correctly predicted the stagflation of the 1970s.