In an influential paper Mankiw, Romer, and Weil (1992) argue that the evidence on the international disparity in per-capita income levels and growth rates is consistent with a standard Solow model, once it has been augmented to include human capital as an accumulable factor. In a study on...

We consider a two-period duopoly characterized by a one-way spillover structure in process R&D and a very broad specification of product market competition. We show that a priori identical firms always engage in different levels of R&D, at equilibrium, thus giving rise to an innovator/imitator...