Slumps and spontaneous remission (wonkish) - Paul Krugman Blog -

this isn’t your father’s recession — it’s your grandfather’s recession.

And monetary policy, at least in its conventional form, has already reached its limits.

Now, the Great Depression was ended by massive fiscal expansion, in the form of World War II. Maybe that will happen again; but so far policy seems inadequate to the task, and the political environment raises concerns about whether we’ll be able to do much more.

Maybe it’s time to dust off Keynesian business cycle theory.

In the long run, we will have a spontaneous economic recovery, even if all current policy initiatives fail. On the other hand, in the long run …

Use, delay, and obsolescence - Paul Krugman Blog -

And Keynes explained why: in the absence of an effective monetary or fiscal policy, a recession would have to go on until

the shortage of capital through use, decay and obsolescence causes a sufficiently obvious scarcity to increase the marginal efficiency

So this could go on for a long, long, long, long time.

Paul Krugman's Introduction to Keynes' General Theory