The Legacy of Knut Wicksell to Capital Theory

Wicksell's contributions to capital theory focused on stationary states in four distinct models intended to account for the time dimension of production in market economies. We now have a better understanding of the true challenges because of two developments: a full theory of intertemporal general equilibria and a methodology for comparative analysis as explained by Hicks. In Wicksell's equilibria, the real interest rate turns out to be equal to the marginal productivity of the volume of social capital, a concept that Wicksell could not master and hence avoided. Challenges remain, particularly regarding the best way to account for complementarities and substitutions over time.