The paper never written: Sraffa, the isoquant and the marginal shepherd

This paper examines a previously unexplored episode in the early history of the isoquant. In some of his unpublished manuscripts of the late 1920s, Piero Sraffa proposed the use of indifference curves within production theory. He found Marshall’s response to Hobson (1909), and more broadly Marshall’s wage theory based on marginal magnitudes, unconvincing. In Sraffa’s view, this approach obscured the relationship between the marginal productivity of a given factor and the ratio of variable to fixed factors. For Sraffa applying indifference curves to production theory would help clarify the genesis and behaviour of the marginal productivity of a given factor.