Syll quotes Roger Farmer:
The NK economist accepts Milton Friedman’s concept of the natural rate of unemployment which asserts that, in the long run, there is a unique equilibrium level of unemployment associated with stable inflationary expectations. If inflation appears, following a recession, a policy maker who accepts NK economics will infer that the economy is operating above potential. If unemployment is now 6%, rather than 3%, it must be that the natural rate of unemployment has increased.
Okay, but why has the natural rate of unemployment increased? Sunspots?
C'mon, Jack. Something must have caused it.