Two-sector growth, optimal growth, and the turnpike: Amalgamation and metamorphosis

This paper deals with the development of growth models from the optimal one-sector neoclassical approach of Cass-Malinvaud-Koopmans vintage, through two-sector, multisector, and turnpike models, and proceeds to discuss their displacement by the single-sector stochastic growth model. We also focus on the definitional shift regarding the turnpike. This is done by surveying both unpublished and published work by Uzawa, Cass, Koopmans, and McKenzie regarding growth and the turnpike, the cross-fertilization between them, and how this brought about the conflation of optimality and the turnpike, and the metamorphosis of the notion of the turnpike, from that of Dorfman-Samuelson Solow, to the Koopmans-McKenzie amalgam of models. Finally, the appearance of endogenous growth models, based on the work of Shell and Uzawa, is dealt with.