This study explores the role of U.S. ethnic scientific and entrepreneurial communities for international technology transfer to their home countries. U.S. ethnic researchers are quantified through an ethnic-name database and individual patent records. International patent citations confirm knowledge diffuses through ethnic networks, and manufacturing output in foreign countries increases with an elasticity of 0.1–0.3 to stronger scientific integration with the U.S. frontier. Specifications exploiting exogenous changes in U.S. immigration quotas address reverse-causality concerns. Exercises further differentiate responses by development stages in home countries. Ethnic technology transfers are particularly strong in high-tech industries and among Chinese economies.

We model spatial clusters of similar firms. Our model highlights how agglomerative forces lead to localized, individual connections among firms, while interaction costs generate a defined distance over which attraction forces operate. Overlapping firm interactions yield agglomeration clusters that are much larger than the underlying agglomerative forces themselves. Empirically, we demonstrate that our model’s assumptions are present in the structure of technology and labor flows within Silicon Valley. Our model further identifies how the lengths over which agglomerative forces operate influence the shapes and sizes of industrial clusters; we confirm these predictions using variations across patent technology clusters.