I. Introduction, 581. — II. Data, 583. — III. Effects of population change, 587. — IV. Causes of population change, 590. — V. Econometrics: testing and estimation, 594. — VI. The estimated model: comparative statics, 599. — VII. The estimated model: dynamics, 600. — VIII. Conclusions, 604. — Appendix: basic data series, 606.