Sims is not Sargent

Below Steve's comment on Sims. Worth a whole post.

Chris Sims' classic 1980 paper "Macroeconomics and Reality" still echoes, or should, among macro model builders and macro econometricians. He could not possibly be clearer about the "incredible" restrictions that models often impose, and proposed a way forward, the VAR in its many forms.

That method has evolved to the point where, for example, good econometricians can recast a DSGE model in VAR form and see if it survives the data. Often they don't, a recent example being Peter Ireland's DSGE so soundly rejected by Katarina Juselius.

The rub is in the qualifier good. This is not easy stuff to do correctly. But its power is worth the sweat. Sims has been homaged over his prize by Mark Thoma here, and by Jim Hamilton, the time series bible author here.

A very favorite story is when Sims, Robert Litterman, and Thomas Doan, all either at the Minneapolis Fed or U of Minnesota in the 80's, "took on" their big models with a small VAR and outforecast them by a bunch. They soon left, maybe excommunicated? But Sims and Litterman at least landed on their feet...Litterman just retired as head statistician at Goldman Sachs. So the Sims triumph validates a reality first approach, meaning data before theory, and with the tools we now have and careful work, this method will become ever more influential in applied macro. Sims has also contributed to Bayesian approaches to macro modeling.

I totally miss the logic of the pairing with Sargent, but such is academic politics.

I agree.

PS: Links are there in the two here in Steve's post, and in the title of Sim's paper and Juselius name.

Esther-Mirjam Sent on Sargent and more

As Kevin Gallagher noted, the contributions of Sargent and Sims are quite different and should be analyzed separately. Ester Mirjam-Sent is certainly the most qualified and discerning critic of Sargent's work, and anybody interested in understanding his (Sargent's) contributions to economics should read her extensive research on his ideas. A good start is her paper in the Cambridge Journal of 1997 (here).

Her concerns are more with the evolution of his thinking about rationality, from rational to bounded, which is a central pillar of neoclassical economics. She notes that Sargent's preoccupation with rationality (which should be contrasted with Simon's views) was to strengthen the theoretical foundations of neoclassical economics. I tend to be more concerned with the critique of those foundations, rather than with the question of how rational behavior leads (or not) to efficient market results.

One important area, in which I have done some research, is hyperinflation theory. Sargent basically is responsible for extending the Cagan model (his classic paper is here) and suggesting that beyond a monetary reform, a credible fiscal adjustment was essential for stabilization. In that sense, while Sargent maintained the fiscal fundamentals of hyperinflation, he suggested that expectations did have a role to play. As Carlos Bastos reminded me recently, here is a critique of Sargent's contribution published in the Economic Journal (subscription needed; portuguese version here). For an alternative discussion of inflation/hyperinflation go here, and for a survey of the literature here.

PS: Sent was one of the faculty members that left Notre Dame after the administration dismantled the heterodox program there. For more on that read here.

Re-writing history

By the way, in the middle of the several comments praising the winners of the Sveriges Riksbank Prize in Economics there will be a lot of misplaced acclaim. Here is one example from the Huffington Post:

"Sargent famously weighed in on the fight against inflation in the early 1980s. Many economists believed it would take years of high interest rates to bring inflation down. But Sargent believed that inflation could be tamed much faster if the Federal Reserve acted enough to break the public's expectations that prices would continue to rise rapidly. That is basically what happened: Then-Fed Chairman Paul Volcker raised interest rates so quickly and so much that inflation expectations were shattered."

So now, if you believe this report, Sargent and Lucas were right about the costless disinflation of the 1980s. Forget that disinflation had to do with falling commodity prices, caused by the hike in interest rates, and with the weakening of the labor force, which faced what was, in the US up to that point, the worse recession since the Great Depression. Unemployment in the US reached 11%, but it was inflationary expectations that mattered. And the Huff Post is a progressive site, isn't it?!

A beautiful blind

Sylvia Nasar wrote a new book (the old and famous was the one on Nash's mind and life) on the history of economic ideas. Robert Solow is not too happy, since he thinks the book is superficial, and spends too much time on the economists lives and on what he thinks are second rate minds (e.g. Beatrice Webb, and I suspect for him Joan Robinson too). I did not finish reading the book, and hence will not review it here now, but I can comment on Solow's review, which is quite misguided.

In fact, the preoccupation with policy issues and the general context in which theories are developed is one of the good aspects of this book. In this sense, Nasar's book is in the direct line of descent of those, like Robert Heilbroner, that think that economics is (and should be) about the great questions (accumulation and the wealth of Nations, the quintessential themes of classical political economy) and that the economist's vision is as essential as, if not more so, than the analytical tools utilized.

For example, Solow complains that the book does not spend enough time discussing the theoretical achievements of Alfred Marshall. The fact, that somebody, with Solow's credentials, can write that after Piero Sraffa's devastating critique of Marshallian partial equilibrium (still in all textbooks, by the way), as if his technical achievement was not simply incoherent and irredeemably incorrect is a testimony about the poor state of our discipline.

Solow's complaints about Nasar discussion of Keynes are more puzzling, since he should be as neoclassical synthesis Keynesian be very comfortable with the 'developments' of Keynesian theory within the mainstream, which are after all the dominant model (the New Keynesian model with an IS, a monetary rule and a Phillips curve). He was instrumental in the creation of the current macroeconomic consensus, and his growth model (for which he won the Sveriges Riksbank Prize, also known as the Nobel in economics, although it's not one of the original Nobels) is the dominant view on growth. If the profession has failed, Solow is certainly responsible for it to a great extent.

If anything the problem with the book is that it shares with the mainstream (including Solow) a certain view of economics, and progress in the discipline, that has been established since the rise of marginalism in the latter part of the 19th century. In this view, there is a direct line of descent from Smith and Ricardo to Marshall (via Stuart Mill) to modern economics. According to this approach, the critical authors are, not the true heirs to classical political economy (that is from Smith/Ricardo to Keynes/Kalecki, via Marx), but critics of some aspects of capitalism that seem to have more heart than brains.

In all fairness, however, it's not surprising that a journalist/writer that is not an specialist economist buys the conventional wisdom on the history of ideas. The conventional history of ideas texts are fundamentally, like the parable in Bruegel's painting, written by blind professors to guide their blind students.

PS: The Sveriges Riksbank has been awarded to two professors (Sargent and Sims) that most likely believe that government intervention in the middle of the crisis is worse than some version of laissez faire. This is the reason, not the predictions about the end of times, why this is a dismal science.