The availability of rich ?rm-level data has led researchers to uncover new evidence on the effects of trade liberalization. First, trade openness forces the least productive fi?rms to exit the market; secondly, it induces surviving fi?rms to increase their innovation efforts; thirdly, it...

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...