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.

This paper quantifies the contribution of technology gaps to international income inequality. I develop an endogenous growth model where cross-country differences in R&D efficiency and cross-industry differences in innovation and adoption opportunities together determine equilibrium technology gaps, trade patterns, and income inequality. Countries with higher R&D efficiency are richer and have comparative advantage in more innovation-dependent industries. I calibrate R&D efficiency by country and innovation dependence by industry using R&D, patent, and bilateral trade data. Counterfactual analysis implies technology gaps account for one-quarter to one-third of nominal wage variation within the OECD.

The evidence for the United States points to balanced growth despite falling investment-good prices and a less-than-unitary elasticity of substitution between capital and labor. This is inconsistent with the Uzawa Growth Theorem. We extend Uzawa's theorem to show that the introduction of human capital accumulation in the standard way does not resolve the puzzle. However, balanced growth is possible if education is endogenous and capital is more complementary with schooling than with raw labor. We present a class of aggregate production functions for which a neoclassical growth model with capital-augmenting technological progress and endogenous schooling converges to a balanced growth path.

Financial development is critical for growth, but its microdeterminants are not well understood. We test leading theories of low demand for financial services in emerging markets, combining novel survey evidence from Indonesia and India with a field experiment. We find a strong correlation between financial literacy and behavior. However, a financial education program has modest effects, increasing demand for bank accounts only for those with limited education or financial literacy. In contrast, small subsidies greatly increase demand. A follow‐up survey confirms these findings, demonstrating that newly opened accounts remain open and in use 2 years after the intervention.