We document two key patterns of structural change: premature deindustrialization and rising industry polarization. Using a dynamic open‐economy model with sector‐biased technological change (SBTC), we evaluate the role of trade in these shifts. Trade alone does not cause premature deindustrialization, but its interaction with SBTC—transmitting global technological change, amplifying the decline in manufacturing's relative price over time, and generating manufacturing trade imbalances across countries—deepens premature deindustrialization over time. Industry polarization, by contrast, emerges only through trade‐driven specialization, as countries diverge along lines of comparative advantage.

Unlike the prediction of a frictionless open economy model, long-term average savings and investment rates are highly correlated across countries—a puzzle first identified by Feldstein and Horioka (1980). We quantitatively investigate the impact of two types of financial frictions on this correlation. One is limited enforcement, where contracts are enforced by the threat of default penalties. The other is limited spanning, where the only asset available is noncontingent bonds. We find that the calibrated model with both frictions produces a savings–investment correlation and a volume of capital flows close to the data. To solve the puzzle, the limited enforcement friction needs low default penalties under which capital flows are much lower than those in the data, and the limited spanning friction needs to exogenously restrict capital flows to the observed level. When combined, the two frictions interact to endogenously restrict capital flows and thereby solve the Feldstein–Horioka puzzle.