Keynes and Sraffa on the concept of "commodity rate of interest"

In general, economists interested in the concept of commodity rate of interest have not noticed that the definitions given by Sraffa in his 1932 review of Hayek’s Prices and Production and by Keynes in his General Theory were not the same. But two letters sent by Keynes to Sraffa in December 1931 give us a hint to see the differences between the ways they approached the subject. In this paper we consider these letters, examine the peculiarities of Sraffa’s approach, and discuss the definition of commodity rates of interest put forward by Keynes both in his 1931 discussion with Sraffa and in Chapter 17 of his General Theory.

Il saggio considera le differenze, solitamente trascurate, nelle definizioni di "tasso proprio di interesse" fornite da Sraffa e Keynes rispettivamente nel 1932 (nel suo saggio su Hayek) e nel 1936 (nella "Teoria Generale").