The era of cheap money shows no one knows how monetary policy works

Monetary policy is supposed to work like this: cut interest rates, and you’ll encourage businesses and households to borrow, invest and spend. It’s not really playing out that way.

In the cheap-money era, now into its second decade in most of the developed world (and third in Japan), there’s been plenty of borrowing. But it’s been governments doing it.

The numbers help explain a growing sense that central banks, which took emergency action to pull economies out of the 2008 slump, may not be able to repeat the trick in another downturn.

They’re even facing broader questions about their independence from politics, a