Dynamic Selection: An Idea Flows Theory of Entry, Trade, and Growth *

Abstract This article develops an idea flows theory of trade and growth with heterogeneous firms. Entrants learn from incumbent firms, and the diffusion technology is such that learning depends not on the frontier technology, but on the entire distribution of productivity. By shifting the productivity distribution upward, selection causes technology diffusion, and in equilibrium this dynamic selection process leads to endogenous growth without scale effects. On the balanced growth path, the productivity distribution is a traveling wave with a lower bound that increases over time. The free entry condition implies trade liberalization must increase the dynamic selection rate to offset the profits from new export opportunities. Consequently, trade integration raises long-run growth. Dynamic selection is a new source of gains from trade not found when firms are homogeneous. Calibrating the model implies dynamic selection approximately triples the gains from trade compared to heterogeneous firm economies with static steady states.