What is the impact of modern transportation technology on long-run economic change in poor countries with high trade costs?  Rail construction in colonial Sub-Saharan Africa provides a natural experiment: 90% of African rail-road lines were built before independence, in a context where...

In this paper, I study the welfare properties of growth models with endogenous innovation, knowledge externalities, and monopoly pricing of new goods. Since useful policy prescriptions cannot be inferred from a balanced growth analysis, welfare is analyzed for transition paths. I provide a...