(Nikki Kahn/The Washington Post)

Lawrence H. Summers, the Charles W. Eliot university professor at Harvard, is a former treasury secretary and director of the National Economic Council in the White House. He is writing occasional posts, to be featured on Wonkblog, about issues of national and international economics and policymaking.

On his blog, Paul Krugman suggests that I have had some kind of change of heart on secular stagnation and converged towards his point of view, citing the publication of the transcript of a 2011 debate which we both participated in. I certainly appreciate the gravity of the secular stagnation issue more than I did a few years ago, given the continuing decline in global real interest rates. But I think Paul exaggerates the change in my views considerably.

The topic of the debate was: “North America faces a Japan-style era of high unemployment and low growth." Paul argued in favor. I opposed the motion — not on the grounds that the U.S. economy was in good shape, but on the grounds that our demand deficiency problems should be easier to solve than Japan’s.

Quoting from my response to Paul’s arguments at the debate:

You’re right the United States has a serious demand deficiency. You’re right that not enough is being done to contain that demand deficiency. You’re right that we will suffer needless unemployment and stagnation until more is done to address that demand deficiency...

My thesis is that as serious as that problem is, it is dimensionally much less than the problems that Japan faced in four respects. Japan’s problems were different in magnitude, different in the depth of their structural roots, different in the relative perspective they had — relative to the rest of the world — and different in the degree of resilience their system had for adapting to them...

It will take time. There are steps that need to be taken but we are a society that works. We are a society whose principal problems -- we all up here agree -- can be addressed by a change in the printing of money and the creation of infrastructure.

Paul responded in part by saying:

The question is, are we going to be stuck in a state of depressed demand of the kind that Larry has talked about. Larry and I agree that that is what has been happening… I think Larry and I agree almost entirely on the economics, on what needs to be done”.

(Full transcript available here).

So, I think we have both been focused on demand and the liquidity trap for a long time.

But there are two areas where I have had somewhat different views from Paul. First, I believe that structural issues are often important for demand and growth. I have often asserted that "business confidence is the cheapest form of stimulus," and once quoted to President Obama the famous 1938 letter by Keynes to Roosevelt:

Businessmen … are … at the same time allured and terrified by the glare of publicity, easily persuaded to be ‘patriots’, perplexed, bemused, indeed terrified, yet only too anxious to take a cheerful view, vain perhaps but very unsure of themselves, pathetically responsive to a kind word. You could do anything you liked with them, if you would treat them (even the big ones), not as wolves or tigers, but as domestic animals by nature, even though they have been badly brought up and not trained as you would wish… If you work them into the surly, obstinate, terrified mood, of which domestic animals, wrongly handled, are so capable, the nation’s burdens will not get carried to market; and in the end public opinion will veer their way.”

Second, I have never related well to Paul’s celebrated liquidity trap analysis. It has always seemed to me be a classic example of economists’ tendency to "assume a can opener." Paul studies an economy in liquidity trap that will, by deus ex machina, be lifted out at some point in the future. He makes the point that if you assume sufficiently inflationary policy after this point, you can drive ex ante real rates down enough to stimulate the economy even before the deus ex machina moment.

This is true and an important insight. But it seems to elide the main issue. Where is the deus ex machina? Where is the can opener? The essence of the secular stagnation and hysteresis ideas that I have been pushing is that there is no assurance that capitalist economies, when plunged into downturn, will, over any interval, revert to what had been normal. Understanding this phenomenon and responding to it seems the central challenge for macroeconomics in this era.

Any analysis that assumes restoration of previous equilibrium is, from this perspective, missing the main issue. I was glad to see Paul recognize this point recently.  I suspect it will lead to more emphasis on fiscal rather than monetary actions in depressed economies.