というエッセイをアーノルド・クリングがNational Affairs書いている(H/T Mostly Economics、原題は「How Effective is Economic Theory?」)。

Instead of "science," we might want to think about economics in terms of "effective theory." As explained by Harvard physicist Lisa Randall,

Effective theory is a valuable concept when we ask how scientific theories advance, and what we mean when we say something is right or wrong. Newton's laws work extremely well. They are sufficient to devise the path by which we can send a satellite to the far reaches of the Solar System and to construct a bridge that won't collapse. Yet we know quantum mechanics and relativity are the deeper underlying theories. Newton's laws are approximations that work at relatively low speeds and for large macroscopic objects. What's more is that an effective theory tells us precisely its limitations — the conditions and values of parameters for which the theory breaks down. The laws of the effective theory succeed until we reach its limitations when these assumptions are no longer true or our measurements or requirements become increasingly precise.

Whereas the term "science" often is used to connote absolute truth in an almost religious sense, effective theory is provisional. When we are certain that in a particular context a theory will work, then and only then is the theory effective.
Over the last 50 years, questions about the effectiveness of economic theory have revolved around five interlocking subjects in particular: mathematical modeling, homo economicus, objectivity, testing procedures, and the particular status of the sub-discipline of macroeconomics.




Structure of Economic Science: Essays on Methodology

Structure of Economic Science: Essays on Methodology


  • 数学モデルに対する信頼性は1980年頃にピークを迎えたが、現在ではかつてほどの信頼は寄せられていない。
  • 行動経済学の発展によって、経済学者はかつてほどホモ・エコノミクスの合理性のモデル化に執着しなくなった。
  • 客観性については、最近、ポール・ローマーの数学もどき批判があった*2
  • 検証過程については、モデルに対するルーカス批判もさることながら、Edward Leamerの「Let's Take the Con Out of Econometrics」(1983)論文*3による計量経済学における検証の恣意性への批判がより重大な影響を与えた。現在では自然実験や実験経済学が主流となっており、かつての重回帰が主流の時代とは様変わりした。
  • スタグフレーションによってマクロ経済学は危機を迎えた。即ち、ケインズ経済学はその有効性が疑問視されるようになった。しかし、大平穏期を経て、金融政策を重視する形で一応のコンセンサスに達した。金融危機後も、危機から得られた知見を取り込む形でコンセンサスを維持している。


Although economics is not now in a state of abject crisis, as it was in the late '70s, it is nonetheless likely to be entering a period of great change on all five of the disciplinary challenges we have been tracing.
First, there is reason to believe that in the coming years economists will reluctantly come to recognize the importance of mental-cultural factors as determinants of economic outcomes, reducing the power of mathematical modeling as an approach.
Second, and very much related to the likely decline in the prominence of modeling, economists are likely also to reluctantly come to recognize that, because cultural factors matter, the simple model of the individual homo economicus has only limited applicability.
Because ideas and cultural context matter, there are many potential causal factors in economic phenomena. Those curmudgeons who argued that economics is not a "closed system" were correct. It is up to each economist to choose which causal factors to study and which to ignore. Unfortunately, this means that it is possible for different economists to arrive at — and to stick with — different conclusions based on predilections.
And this points to the third plausible development in economic theory. There is a very real possibility that over the next 20 years academic economics will congeal into a discipline, like sociology today, which is definitively shaped by an ideologically driven point of view.
Fourth, it seems unavoidable that economists will reluctantly come to recognize that they deal in the realm of patterns and stories, rather than decisive hypothesis testing. It simply isn't possible for economists and other social scientists to achieve the same rigor as is found in the natural sciences, and economists seem increasingly to be accepting this reality. One favorable sign is the increased focus on replicability of empirical work in economics.

Finally, we come to the special case of macroeconomists, who were in an acknowledged state of crisis in 1980 but are oddly complacent today. My own view is that the attempt to interpret economic phenomena in aggregative terms, as if all workers were identical and all investment were in machinery, is proving untenable. ...
A few economists, led by Daron Acemoglu, have started to look at industry linkages. They are finding that various industry clusters respond to events in different ways. This increasing study of divergence could point toward the death of macroeconomic modeling as I learned it in graduate school and as it has until recently been taught.

*1:cf. ここ

*2:cf. ここ

*3:cf. ここ

*4:前掲書に寄稿したEmile GrunbergとKenneth Bouldingや、1980年のThe Public Interest(National Affairsの「前身」)特集号邦訳)「The Crisis in Economic Theory」に寄稿したダニエル・ベルを指すと思われる。