Random utility models are widely used to study consumer choice. The vast majority of applications assume utility is linear in consumption of the outside good, which imposes that total expenditure on the subset of goods of interest does not affect demand for inside goods and restricts demand...

We study the gains from trade in a model with oligopolistic competition, heterogeneous firms and innovation, and provide a formula to decompose the mechanism. The new insight we provide is that market concentration can be a welfare-relevant feature of market power above and beyond markup...