と題した先月末(6/29)のEconomist's Viewエントリで、Mark Thomaが3つのブログエントリを紹介している


High-status economists' disdain for popularizing is baseless. Once you understand Bayes' Rule, you realize that "definitive proof" of empirical claims is neither possible nor necessary. All any mortal can do is begin with common sense, then update his beliefs if and when some evidence arrives. Indefinitely suspending judgment is not just overly cautious; it's irrational.


Four years after a huge deflationary shock with no apparent shock to technology, asset-pricing papers and labor search papers and international finance papers and even some business-cycle papers continue to use models in which business cycles are driven by technology shocks. No theory seems to have been thrown out. And these are young economists writing these papers, so it's not a generational effect. ...

If smart people don't agree, it may because they are waiting for new evidence or because they don't understand each other's math. But if enough time passes and people are still having the same arguments they had a hundred years ago - as is exactly the case in macro today - then we have to conclude that very little is being accomplished in the field. The creation of new theories does not represent scientific progress until it is matched by the rejection of failed alternative theories.

The root problem here is that macroeconomics seems to have no commonly agreed-upon criteria for falsification of hypotheses. Time-series data - in other words, watching history go by and trying to pick out recurring patterns - does not seem to be persuasive enough to kill any existing theory. Nobody seems to believe in cross-country regressions. And there are basically no macro experiments. ...

So as things stand, macro is mostly a "science" without falsification. In other words, it is barely a science at all. Microeconomists know this. The educated public knows this. And that is why the prestige of the macro field is falling. The solution is for macroeconomists to A) admit their ignorance more often (see this Mankiw article and this Cochrane article for good examples of how to do this), and B) search for better ways to falsify macro theories in a convincing way.


このノアピニオン氏とは自分は少し見方が違う、としてThomaが3番目にリンクしたのが、自らの昨年のThe Fisacal Times論説記事である。

This divide in the profession also increases the possibility that the public will be sold false or misleading ideas intended to promote an ideological or political agenda. If the experts disagree, how is the public supposed to know what to believe? They often don’t have the expertise to analyze policy initiatives on their own, so they rely on experts to help them. But when the experts disagree at such a fundamental level, the public can no longer trust what it hears, and that leaves it vulnerable to people peddling all sorts of crazy ideas.
When the recession began, I had high hopes that it would help us to sort between competing macroeconomic models. As noted above, it's difficult to choose one model over another because the models do equally well at explaining the past. But this recession is so unlike any event for which there is existing data that it pushes the models into new territory that tests their explanatory power (macroeconomic data does not exist prior to 1947 in most cases, so it does not include the Great Depression). But, disappointingly, even though I believe the data point clearly toward models that emphasize the demand side rather than the supply side as the source of our problems, the crisis has not propelled us toward a particular class of models as would be expected in a data-driven, scientific discipline. Instead, the two sides have dug in their heels and the differences – many of which have been aired in public – have become larger and more contentious than ever.