R&D Models of Economic Growth and the Long-Term Evolution of Productivity and Innovation

The article suggests that the failure of many R&D growth models to reconcile the stylized facts of a constant productivity growth, and of a long-term rise of R&D employment share, can be intrepreted as the result of technological assumptions that make abstraction from complementarity in production. Drawing upon a system-like view of technology, which owes much to the contriburions of Nathan Rosenberg, Joel Mokyr, and many others, and can be traced back to Karl Marx, the article argues that the stylized facts above can be explained by the strict relation between the arrival of new technologies and the growth of variety.