As many people have pointed out, the Trump tax represented a total break with the normal principles of fiscal policy. Historically, we’ve tended to run big deficits when the economy is weak, smaller deficits or surpluses when it’s strong. But now the deficit is soaring even in the face of low unemployment. This is irresponsible, and shows that Republican handwringing over deficits was always phony – which some of us pointed out at the time.

But something that has been pointed out less is that this is actually part of a broader story: fiscal policy has been off the rails since 2010, not because of what it has done to the national debt, but because of what it has done to the macroeconomy.

Here’s what fiscal policy should do: it should support demand when the economy is weak, and it should pull that support back when the economy is strong. As John Maynard Keynes said, “The boom, not the slump, is the right time for austerity.” And up until 2010 the U.S. more or less followed that prescription. Since then, however, fiscal policy has become perverse: first austerity despite high unemployment, now expansion despite low unemployment.