I'm reading/using his textbook this summer...

Changeless economy

Economics is a field where the information changes little from year to year? I’m currently revising the macroeconomic chapters — and everything has changed. We’ve gone from a world in which recessions were mostly generated by the Fed to control inflation to a world in which bursting financial bubbles lead the way, from a world in which discretionary fiscal policy was considered uncouth to one in which both parties feel it’s essential, from a world in which central banks were considered omnipotent to one in which my former department chairman is trying desperately to get some traction — and all of this has happened in just a few years.
I think they could have picked a better example.