Why did austerity fail? The Poor Behave Differently From the Rich:

 models failed to predict the consequences of the austerity programs that several European countries adopted in 2010. It turned out that actual people didn’t behave like the imaginary proxy. Economists are learning that the poor and the wealthy respond differently to austerity and stimulus. This could present challenges to politicians. If people behave differently, then policy might have to treat them differently.

Austerity was doomed from the start.