This paper embeds firm dynamics into the Neoclassical model and provides a simple framework to solve for the transitional dynamics of economies moving towards more selection. As in the Neoclassical model, markets are perfectly competitive, there is only one good and two production factors...

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...