Evans and Honkapohja: Your papers on monetary history look very different than your other work. Why are there so few equations and so little formal econometrics in your writings on economic history? Like your “Ends of Four Big Inflations” and your paper with Velde on features of the French Revolution? We don’t mean to insult you, but you look more like an “old economic historian” than a “new economic historian.”

Sargent: This is a tough question. I view my efforts in economic history as pattern recognition, or pattern imposition, exercises. You learn a suite of macroeconomic models that sharpen your mind by narrowing it. The models alert you to look for certain items, e.g., ways that monetary and fiscal policy are being coordinated. Then you read some history and economic history and look at a bunch of error-ridden numbers. Data are often error-ridden and incomplete. You read contemporaries who say diverse things about what is going on, and historians who put their own spins on things. From this disorder, you censor some observations, overweight others. Somehow, you impose order and tell a story, cast in terms of the objects from your suite of macroeconomic theories. Hopefully, the story rings true.

Evans and Honkapohja: Do you find rational expectations models useful for understanding history?

Sargent: Yes. A difficult thing about history is that you are tempted to evaluate historical actors’ decisions with too much hindsight. To understand things, you somehow have to put yourself in the shoes of the historical actor and reconstruct the information he had, the theory he was operating under, and the interests he served. Accomplishing this is an immense task. But our rational expectations theories and decision theories are good devices for organizing our analysis. By the way, to my mind, reading history immediately drives you away from perfect foresight models toward models in which people face nontrivial forecasting problems under uncertainty.

Evans and Honkapohja: Interesting. But you didn’t answer our question about why your historical work is more informal than your other work.

Sargent: I don’t know. Most of the historical problems that I have worked on have involved episodes that can be regarded as transitions from one rational expectations equilibrium to another. For example, the ends of hyperinflations; the struggles for new monetary and fiscal policies presided over by Poincare and Thatcher; the directed search for a new monetary and fiscal constitution by a sequence of decision makers during the French Revolution; the eight-hundred-year coevolution of theories and policies and technologies for producing coins in our work with François on small change. I saw contesting theories at play in all of these episodes. We didn’t see our way clear to being as complete and coherent as you have to be in formal work without tossing out much of the action. Analyzing the kinds of the transitions that we studied in formal terms would have required a workable model of the social process of using experience to induce new models, paradigm shifts and revolutions of ideas, the really hard unsolved problem that underlies Kreps’s anticipated utility program. (You wouldn’t be inspired to take Muth’s brilliant leap to rational expectations models by running regressions.) We didn’t know how to make such a model, but we nevertheless cast our narratives in terms of a process that, with hindsight, induced new models from failed experiences with old ones.


Evans and Honkapohja
貨幣の歴史に関する論文は、あなたの他の論文とは随分違うように思われます。経済史に関するあなたの論文には、なぜ方程式や正規の計量経済学があまり無いのでしょうか? 「四大インフレーションの終焉」*1や、ヴェルデとのフランス革命の特徴に関する論文*2がそうですよね? 侮辱の意図はありませんが、あなたは「新しい経済史家」ではなく「古い経済史家」のように見えます。
Evans and Honkapohja
Evans and Honkapohja

*1cf. ここ。邦訳は「合理的期待とインフレーション」所収。

*2cf. ここ

*3cf. Wikipedia

*4cf. 原論文、および書籍(下記)とそのケイトー研究所書評

The Big Problem of Small Change (Princeton Economic History of the Western World)

The Big Problem of Small Change (Princeton Economic History of the Western World)

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