I. The increase in productivity with city size, 393. — II. The labor productivity of cities, 396. — III. The contributions of Hicks-neutral productivity and capital intensity, 401. — IV. The direction of causality, 406. — V. Conclusions, 410. — Appendix A: choice of the industries included in this study, 411. — Appendix B: evidence relating to the capital-labor ratio in cities of different size, 412.

The Heckscher-Ohlin-Vanek model predicts relationships among industry input requirements, country resource supplies, and international trade in commodities. These relationships are tested using data on twelve resources, and the trade of twenty-seven countries in 1967. The Heckscher-Ohlin propositions that trade reveals gross and relative factor abundance are not supported by these data. The Heckscher-Ohlin-Vanek equations are also rejected in favor of weaker models that allow technological differences and measurement errors.

The Heckscher-Ohlin-Vanek model predicts relationships among industry input requirements, country resource supplies, and international trade in commodities. These relationships are tested using data on twelve resources, and the trade of twenty-seven countries in 1967. The Heckscher-Ohlin propositions that trade reveals gross and relative factor abundance are not supported by these data. The Heckscher-Ohlin-Vanek equations among input requirements, resource supplies, and trade are also rejected in favor of weaker models that allow technological differences and measurement errors.