Source: James Tobin, BPEA.





The story is as follows: beginning in 1980:1 the government takes monetary and fiscal measures that gradually reduce the quarterly rate of increase of nominal income, MV. It is reduced in ten years from 12 percent a year to the noninflationary rate of 2 percent a year, the assumed sustainable rate of growth of real GNP. The inertia of inflation is modeled by the average of inflation rates over the preceding eight quarters. The actual inflation rate each quarter is this average plus or minus a term that depends on the unemployment rate, U, relative to the NAIRU, assumed to be 6 percent. This term is (6/U(-1) - 1). It implies a Phillips curve slope of one-sixth a quarter, two-thirds a year at U = 6 and has the usual curvature.

This is not a prediction! It is a cautionary tale. The simulation is a reference path, against which policymakers must weigh their hunches that the assumed policy, applied resolutely and irrevocably, would bring speedier and less costly results. There are several reasons that disinflation might occur more rapidly. When unemployment remains so high so long, bankruptcies and plant closings, prospective as well as actual, might lead to more precipitous collapse of wage and price patterns than have been experienced in the United States since 1932. Moreover, the very threat of a scenario like figure 6 may induce wage-price behavior that yields a happier outcome. A simulated scenario with rational rather than adaptive expectations of inflation would show speedier disinflation and smaller unemployment cost, to a degree that depends on the duration of contractual inertia, explicit or implicit.

Steve Williamson has a very nice post " Historical Fiction ", rebutting the claim, largely by Paul Krugman, that the late 1970s Keynesian macroeconomics with adaptive expectations was vindicated in describing the Reagan-Volker era disinflation.The claims were startling, to say the least, as they sharply contradict received wisdom in just about every macro textbook: The Keynesian IS-LM model, whatever its other virtues or faults, failed to predict how quickly inflation would take off in the 1970, as the expectations-adjusted Phillips curve shifted up. It then failed to predict just how quickly inflation would be beaten in the 1980s. It predicted agonizing decades of unemployment. Instead, expectations adjusted down again, the inflation battle ended quickly. The intellectual battle ended with rational expectations and forward-looking models at the center of macroeconomics for 30 years.Just who said what in memos or opeds 40 years ago is somewhat of a fodder for a big blog debate, which I won't cover here.Steve posted a graph from an interesting 1980 James Tobin paper simulating what would happen. This is a nicer source than old memos or opeds from the early 1980s warning of impeding doom. Memos and opeds are opinions. Simulations capture models.The graph:I thought it would be more effective to contrast this graph with the actual data, rather than rely on your memories of what happened.The black lines are the Tobin simulation. The blue lines are what actually happened. (I'm not good enough with photoshop to superimpose the graphs, so I read Tobin's data off his chart.)The two curves parallel in 81 to 83, with reality moving much faster. But In 1984 it all falls apart. You can see the "Phillips curve shift" in the classic rational expectations story; the booming recovery that followed the 82 recession.And you can see the crucial Keynesian prediction error: After the monetary tightening is over in 1986, no, we do not need years and years of grinding 10% unemployment.So, conventional history is, it turns out, right after all. Adaptive-expectations ISLM models and their interpreters were predicting years and years of unemployment to quash inflation, and it didn't happen.One can debate 1981 to 1983. Here reality followed the general pattern, moving down a Phillips curve. Perhaps that is the success. But the move was much quicker than Tobin's simulation. One might crow that inflation was conquered much more quickly than Keynesians predicted. But perhaps the actual monetary contraction may have been larger than what Tobin assumed, and assuming a harsher contraction would have sent the economy down the same curve faster?Tobin describes his simulation thus:So, I think the answer is no. A faster monetary contraction leaves the 8 quarter lag of inflation in place, so you'll get even bigger unemployment and not much contraction in inflation. If someone else wants to redo Tobin's simulation with the actual 81-83 inflation, that would be interesting. But it is a bit tangential to the central story, 1984. You can also see here in the highlighted passage (my emphasis) how adaptive expectations are crucial to the story.Now, let's be fair to Tobin. Yes, as quoted by Steve, he came out in favor of "Incomes policies," which used to be a nice euphemism for wage and price controls, but have an even more Orwellian ring these days. But Tobin also wrote, just following this graph,My emphasis. Now, having seen only one big Phillips curve failure in the 1970s, it might be reasonable for policy-oriented people not to jettison their entire theoretical framework in one blow. And this Tobin piece, using adaptive expectations, does incorporate some of the lessons of the 1970s. In the 1960s, Keynesians used a fixed Phillips curve. Friedman famously pointed out that it would not stay fixed -- but even Friedman (1968) had adaptive expectations in mind. For policy purposes it might make sense to integrate over models and adapt slowly, an attitude I just recommended in present circumstances.You can see Tobin clearly seeing the possibilities, and clearly seeing the conclusions that we would come to after seeing the "happier outcome." That he had not come to these conclusions before the fact is understandable.That contemporary commentators should forget or obfuscate this history, in an effort to resuscitate a comfortable, politically convenient, but failed economics of their youth, is less forgivable.I don't want to fully endorse the classic resolution of 1984. Lots of other things changed, in particular deregulation and a big tax reform in the air. There was a lot of new technology. Financial deregulation was kicking in. We may find someday that such "supply side" changes were behind the 1980s boom. And we may jettison or radically reunderstand the Phillips curve, even with the free expectations parameter to play around with. It certainly has fallen apart lately ( here here and many more). But ISLM / adaptive expectations as an eternal truth just doesn't hold up. It really did fail in the 70s, and again in the 80s.PS: The chart using actual inflation FYI