The Origins of Piero Sraffa’s Equations

The paper investigates the origins of the equations which form the structure of Piero Sraffa’s Production of Commodities by means of Commodities. Following an interpretation first developed by Pierangelo Garegnani in a paper that higlighted the importance of a manuscript headed ‘Notes London, Summer 1927 (Physical Real Costs etc.)’, we single out new evidence relevant to the reconstruction of the path which led Sraffa to conceive his equations. In particular, we stress how Sraffa came to pay special attention to the case of a subistence economy (‘a community that produces just what is sufficient to keep it going’) and how this led him to shift his attention from the idea of reducing heterogeneous physical costs to an ‘absolutely necessary commodity’ to the determination of exchange ratios by the solution of systems of simultaneous equations. Furthermore, we suggest that a close background to this analysis may be recognized in an attempt to distinguish cost from income which can be found in manuscripts kept in a folder headed ‘Physical Real Costs’.