John Quiggin has a couple of interesting posts on the topic over at Crooked Timber (image from Wikipedia):
I’ll start with the central issue of macroeconomics, unemployment. It’s the central issue because macroeconomics begins with Keynes’ claim that a market economy can stay for substantial periods, in a situation of high unemployment and excess supply in all markets. If this claim is false, as argued by both classical and New Classical economists, then there is no need for a separate field of macroeconomics – everything can and should be derived from (standard neoclassical) microeconomics.
The classical view is that unemployment arises from problems in labor markets and can only be addressed by fixing those problems. Within the classical camp, Real Business Cycle theory allows for cyclical unemployment to emerge as an voluntary response to technology shocks and changes in preferences for leisure – hence Krugman’s snarky but accurate quip that, according to RBC, the Great Depression should be called the Great Vacation. More generally, on the classical view, long-term unemployment has to be explained by labour market distortions such as minimum wages, unions, restrictions on hiring and firing, and so on.
The RBC school mostly treated the Great Depression as an exceptional case, to be dealt with later, and they have been no better on the Great Recession. While some have tried, it’s obviously silly to explain the current recession as the product of technology shocks in the ordinary sense of the term. If you treat the financial sector meltdown as a technology shock,RBC amounts to little more than the observation that opium makes you sleepy because of its dormitive quality. Since financial sector booms and busts are clearly driven by the the general business cycle, you get the theory that the business cycle is caused by … the business cycle.
Looking at the broader classical view, there are two big problems. First, over the past twenty or thirty years unions have got weaker nearly everywhere, minumum wages have generally fallen in real terms, or at least relative to average wages, and labour markets have been ‘reformed’ to become more flexible. So, you would expect low and falling unemployment. The low rate of US unemployment in the 1990s and (to a lesser extent) 2000s was indeed taken as a vindication of this prediction. So, sharp increases in unemployment are the opposite of what was expected. The even bigger problem is that, since 2008, unemployment has risen sharply in many different countries, with very different institutions. Many of these countries have reacted by cutting social protections (here’s Latvia, for example)[1] but unemployment has remained high.