He writes,
whenever somebody claims to have a deeper understanding of economics (or actually anything) that transcends the insights of simple models, my reaction is that this is self-delusion. Any time you make any kind of causal statement about economics, you are at least implicitly using a model of how the economy works. And when you refuse to be explicit about that model, you almost always end up – whether you know it or not – de facto using models that are much more simplistic than the crossing curves or whatever your intellectual opponents are using.
Pointer from Mark Thoma.
Shorter version: it takes a model to beat a model
I find that persuasive, although I wish we had a less pretentious term than “model,” which makes us sound more scientific than I believe we are. What I would like to do is compare the state of the IS-LM-Phillips Curve model with that of the PSST model. PSST, or patterns of sustainable specialization and trade, says that a sharp rise of unemployment is the result of patterns of trade made unsustainable by changes in technology and/or asset prices, and that only a gradual process of entrepreneurial trial and error can discover new patterns of sustainable specialization and trade. More about this model can be found here (see items 2,3, and 4).
Some comments:
1. I think that both PSST and IS-LM-Phillips are difficult to falsify. In some sense, the macroeconomic data are over-fit, so that the dataset cannot be used to decisively reject one model in favor of another.
2. I would counter one of Krugman’s narrow points, where he says that the liquidity trap explains why the huge reserves in the banking system have not had major effects. If this is true, then why did the Fed need to pay interest on reserves? I assume that the Fed thinks that if they had not paid interest on reserves, then its huge injection of reserves would have caused rapid money growth and high inflation. It would be interesting to poll economists on whether they would agree–my guess is that most would. It seems to me that Krugman would have to say “no” to the poll, but perhaps I am misunderstanding him. I am not sure how I would answer such a poll myself.
3. I do not align myself with those who see the Fed as the prime mover of inflation. My “model” of inflation is a pretty weak one. Basically, I just think that businesses get into habits about how much to raise workers’ wages each year. Maybe those habits are affected by the aggregate unemployment rate, as in the Phillips Curve, but I would caution that we do not have homogeneous “labor.” Some folks can be getting regular raises that are large, while others may fail to get raises at all. Each business looks at its own labor market, not at the economy-wide unemployment rate.
What about the 1970s? I would say that the 1970s were a period of “inflation consciousness.” Everyone became aware of it, and “cost-of-living” raises got built into the system, because so many employers incorporated recent inflation into current wage increases. I am tempted to suggest that the advent of wage-price controls starting in 1971 had the adverse consequence of raising inflation consciousness.
What about hyperinflation? I believe that really, big, long-term inflation is a fiscal phenomenon. That is, the government runs huge deficits, people stop lending to government, and then it meets its deficits with paper claims. We are not at that point in the U.S., but if we ever do reach the point where bond investors lose confidence–watch out.
4. So I have a PSST model for unemployment, and my “weak” model[s] for inflation. I think it is fair to criticize them as “just-so stories.” But I would say the same thing about the sorts of models preferred by Blanchard or Krugman. Just-so stories, dressed up in pretty math.
5. Elsewhere, Krugman writes,
Basically, the new IO [industrial organization, the field of recent Nobel Laureate Jean Tirole] made it OK to tell stories rather than proving theorems, and thereby made it possible to talk about and model issues that had been ruled out by the limits of perfect competition. It was, I can tell you from experience, profoundly liberating.