INETやCIGIの援助を受けてここ数年スラッファの文献研究を続け、昨年以下の本を出版したAjit Sinhaが、表題のINETブログ記事(原題は「Sraffa’s Revolution in Economic Theory」)でその成果を報告している。

A Revolution in Economic Theory: The Economics of Piero Sraffa (English Edition)

A Revolution in Economic Theory: The Economics of Piero Sraffa (English Edition)


It would be, I believe, a mistake to see (as has been sometimes suggested) in Sraffa’s analysis a causal system rival to the standard neoclassical model of the determination of prices, quantities, and the distribution of incomes. Sraffa was changing the nature of the inquiry—toward an important but neglected theme—rather than providing a different answer to a given question already in vogue in contemporary economics. — Amartya Sen (2004, p. 588, emphasis in original).
(時々試みられたように)スラッファの分析の中に、価格、数量、ならびに所得分布の決定についての標準的な新古典派モデルに対抗するような因果関係の体系を見い出そうとするのは誤りである、と私は考える。スラッファは、当時の経済学で既に流行りとなっていた所与の質問に別の答えを出そうとしていたわけではなく、質問の性質を、重要だが無視されていたテーマに変えようとしていたのである。 - Amartya Sen (2004, p. 588, 強調は原文)

そして、ケンブリッジ資本論争においてスラッファの著書「商品による商品の生産(Production of Commodities by Means of Commodities)」が果たした役割を以下のように評している*1

Sraffa’s “re-switching” proposition showed that, in general, there is no logical way by which the “intensity of capital” can be measured independently of the rate of interest — and hence the widely held neoclassical explanation of distribution of income was logically untenable.
This victory was hailed as the crowning glory of Sraffa’s book, but it came at a high price. The orthodoxy interpreted Sraffa’s re-switching proposition as his main contribution to economic theory; they accepted its truthfulness and argued that the modern general-equilibrium orthodox economics need not aggregate capital independently of prices or the rate of interest, and hence the Sraffa critique of the orthodox theory was not fatal but rather minor. ...In a strange way it appeared that Sraffians lost the war after winning the great battle.


...the question of re-switching of techniques was not the central aspect of Sraffa’s pure theory. It is a book that was designed to challenge the orthodox economic theory in a more fundamental way—there lies a methodological and philosophical sub-terrain underneath the apparent economic theory of the book. ...
Actually, the book was designed to challenge the usual mode of theorizing in terms of essential and mechanical causation — prices are shown to be neither ultimately caused by labor or utility/scarcity, nor are they determined by the forces of demand and supply. It, instead, argues for a descriptive or geometrical theory based on simultaneous relations. Sraffa demonstrates that on the basis of observed input-output data of an interconnected system of production, one can show, by simply rearranging them, that the rate of profits of the system can be determined without the knowledge of prices, if the wage rate is given from outside the system. In this context, prices have only one role in the system and that is to consistently account for the given distribution of the net output in terms of wages and the rate of profits (introduction of rent of land does not make any difference to the result). Prices, in this context, do not carry any information that prompts “agents” to adjust their supplies and demands to bring about an equilibrium in the market. The questions of equilibrium as well as market structure are simply irrelevant to the problem.
A consequence of this approach was a complete removal of “agent’s subjectivity” or demand, and “marginal method” or counterfactual reasoning from economic analysis — the two fundamental pillars of orthodox economic theory. What Sraffa’s alternative economic theory establishes is that income distribution in terms of wage rate and the rate of profits are linearly related to each other and can be taken as given independently of prices. Now prices for any given input-output data must be such that those given distributional variables are consistently accounted for — a conclusion that stands in stark opposition to the orthodox economic theory, which maintains that both the size and distribution of income are determined simultaneously with prices. Sraffa’s discovery of the “Standard commodity” plays the central role in establishing this thesis; and his reinterpretation of classical economics is also rooted in the above proposition.


...given a system in a “self-replacing state,” i.e., when all inputs can be deducted from outputs in physical terms, we have in general a physical ratio of net output to total capital of the system that is made up of heterogeneous goods. The value of this ratio can only be found out when physical outputs and capital goods are multiplied by their prices.
The problem is that, in general, variations in r leads to variations in prices, which in turn leads to apparent variations in the value of this ratio. Sraffa, however, finally succeeded in showing that such changes in the net output-capital ratio happen due to the arbitrary nature of the measuring standard. By rearranging (i.e., rescaling) the input-output data of the real system, Sraffa derives another system of inputs and outputs, which, in some sense, represents the average of the given system and is mathematically equivalent to that system. Sraffa called it the Standard system — in this system the aggregate inputs and outputs are made up of same goods occurring in the same proportion, thus the ratio of net output to capital is well defined in physical terms and is independent of prices. The aggregate of the Standard system can be seen as the average industry of the real system in the sense that the ratio of capital to labor of the Standard system represents the average ratio of capital to labor of the real system and that this system produces a composite commodity, which can be characterized as the “average commodity” of the real system. Sraffa called this composite commodity, the Standard commodity and showed that if the Standard commodity is chosen as the standard of measure for measuring prices and the given wages then it can be shown that the ratio of net output to capital remains constant with respect to changes in r. Thus the Standard commodity allows us to see that for any given system the relationship between wages and the average rate of profits is given by: r=R(1-w).


In his endorsement of my book (Sinha 2016), Samuel Hollander puts it thus: “Sinha puts paid thereby to alternative readings of that enigmatic work [Sraffa 1960], including that of the late Pierangelo Garegnani, Sraffa’s student and the leading Sraffian commentator.” After the publication of this book, I hope scholars interested in pure economic theory and history of thought would take a second look at Sraffa’s contribution to economics and see what could be built on the new foundation provided by him.
私の本(Sinha 2016)を推薦した文章でサミュエル・ホランダー*2は次のように書いた:「それによってシンハは、かの謎めいた研究[スラッファ1960]についての他の解釈に終止符を打った。その中には、スラッファの門弟で代表的なスラッファ研究者であるピエランジェロ・ガレニャーニ*3の解釈も含まれる。」 この本の出版を受けて、純粋経済理論と経済学思想史に興味を持つ研究者たちが、スラッファの経済学への貢献を見直し、彼が提供した新たな基盤の上に何が構築できるかを研究することを望みたい。

ただ、コメント欄の3件のコメントのうち2件では手厳しい指摘がなされている。Heretical SraffaことScott Carter*4は、スラッファが行った研究の全貌は未だ明らかになっていないのだから、Sinhaによるスラッファの研究の定義付けも額面通り受け止めることはできない、とコメントしている。Egmont Kakarot-Handtkeというコメンター*5は、スラッファの出版した本はそもそもゴミ箱行きが相応しいのだからそれで新古典派に代わる手法を打ち出そうとするのは不毛な行為であり、真のミクロ的基礎付けを必要とする新古典派の置き換えはSinhaのような無能な研究者の手に余る、と書いている。

*1:cf. 以前のエントリ

*2:cf. Samuel Hollander - Wikipedia

*3:cf. Pierangelo Garegnani - Wikipedia、亡くなる3年前の来日時の写真