A depressing consensus prevailed among economists at the recent AEA/ASSA annual meetings: the developed world is stuck with low growth, low inflation and low interest ratesfor years to come. Even worse, there is no consensus on why.

Supply and demand for goods and services are basic economic concepts. But when it comes to interpreting shocks to either in the real world, things get murky. Some economists blame prevailing conditions in the industrialised world on flagging supply, others on weak demand. Here’s my take, and what to do about it, in the Financial Times.