Regulating polygamy to induce more productive investments and improve women’s rights requires anticipating changes in marital choices and welfare. I develop and estimate a novel theory of polygamy that incorporates an empirical feature previously overlooked: co-wives interact in a senior-junior hierarchy. In equilibrium, single, monogamous, and polygamous households emerge. Optimal female sorting generates co-wives inequality: high skilled women become senior wives in polygamous households with wealthy males and low skilled juniors. The estimated model reproduces the observed equilibrium. A novel policy implication is that in the absence of better outside options from marriage, banning polygamy harms all women. ∗Department of Economics, University of Michigan, 611 Tappan Av., Ann Arbor, MI 48103,
[email protected]. I am extremely grateful to my Phd dissertation advisors Joseph Altonji, Costas Meghir, Larry Samuelson, and Chris Udry for their guidance and support. I am also grateful to Pierre André Chiappori, Scott Kominers, Chiara Margaria, Esteban Peralta, and Bernard Salanié for many productive discussions at various points of this project. I also thank Martha Bailey, Hoyt Bleakley, Tibor Heumann, Sylvie Lambert, Corinne Low, Robert Pollak, Tommaso Porzio, Meredith Startz, Mel Stephens, Fernando Tohme, Alessandra Voena, and seminar participants at Yale University, Columbia University, the Jerusalem School in Economic Theory, and University of Michigan for helpful comments, discussions, and suggestions. All errors are mine.