いわゆるケインジアン経済学の問題をケインズ個人に帰すのは誤りである、という趣旨のデューク大学教授Kevin D. Hooverの論文をMostly Economicsが紹介している


The potted histories of macroeconomics textbooks are typically Keynes-centric. Keynes is credited with founding macroeconomics, and the central developments in the field through the early 1970s, including large-scale macroeconometric models are usually termed “Keynesian.” The story of macroeconomics is framed as support or opposition (e.g., monetarism or the new classical macroeconomics) to Keynes. The real story is more complicated and involves at least two distinct threads. Keynes was important, but perhaps more important for the detailed development of the field were the early macroeconometricians – Ragnar Frisch and Jan Tinbergen. Frisch and Tinbergen adopted physical or mechanical metaphors in which aggregate quantities are central. Keynes’s vision of macroeconomics is better described as “medical.” It is based in human psychology and individual decision-making and sees the economy as an organic system. Whereas policymakers and economic advisers in Keynes view can operate only within the economic system, Frisch and Tinbergen laid the basis for an optimal-control approach to economic policy in which the policymaker stands outside the system. Recent new classical macroeconomics has adopted an uneasy amalgam of the medical and mechanical metaphors.


...it is worth noting that recent macroeconomics can be seen as an attempting reconciliation of the mechanical and organic metaphors. The new classical revolution of the 1970s, although framed as “anti-Keynesian,” was more directly an assault on macroeconometric models in the tradition of Tinbergen and Klein.
New classicals called for models that placed expectations and optimal choice by individuals back in the center of macroeconomic analysis. They rejected the view that the policymaker stands outside the economic system. In these respects they stood closer to Keynes than they realized. But in stressing quantitative and mathematically closed models, they stood firmly in the mechanical tradition of Frisch and Tinbergen. For instance, in a famous passage, Lucas wrote:

Our task . . . is to write a FORTRAN program that will accept specific economic policy rules as “input” and will generate as “output” statistics describing the operating characteristics of time series we care about, which are predicted to result from these policies. [Lucas 1980, p. 288]

Keynes could never have agreed.

我々の仕事は・・・特定の経済政策ルールを「入力」として受け付け、そうした政策の帰結として予測される我々の関心の対象である時系列データの動作特性を捉えた「出力」統計を生成するFORTRANプログラムを書くことだ。[Lucas 1980, p. 288]



Combining individual human decision-making with the mechanical models is difficult. Just as Frisch had observed in 1933, there are too many individuals in the economy. His solution was to invent aggregate macroeconomics. Keynes’s solution was provide only a qualitative analysis of the connection between the individual and the economy as a whole and to adopt the pragmatic stance of the empirically minded physician in matters of policy. The new classicals and their fellow travelers, the new Keynesian, have instead applied highly simplified microeconomic models – models in which one or a few agents stand for, or represent, individual choice – to aggregate data. These are now the most popular models in economics and the ones that have been most vilified by those who believed that the economics profession failed us in the Great Recession.
個人の意思決定を機械的なモデルに結び付けることは難しい。フリッシュが1933年に述べたように、経済における個人は多過ぎるからだ。彼の解決法は、総量を扱うマクロ経済学を発明することだった。ケインズの解決法は、個人と経済全体との関係については定性的な分析に留め、政策については経験主義的な医者の実務的なスタンスを適用する、というものだった。新しい古典派やそれと同系統であるニューケインジアンは、総量データに非常に単純化されたミクロ経済学モデル―― 一人ないし数人の主体が個人の選択を表現ないし代表するようなモデル――を適用する、という方法を採った。そうしたモデルは今や経済学で最も一般的なモデルであり、かつ、大不況において経済学者がヘマをしたと考える人たちから最も非難されてきたモデルである。