William Lavely's research interests include fertility, Chinese society, marriage and the family, household structure, and family change in context. He has written on Chinese historical demography, rising sex ratios, and Chinese censuses. His historical work, which concerns the proximate determinants of China prior to demographic transition, highlights the role of breastfeeding duration and coital frequency in explaining low levels of marital fertility in late imperial China as compared to early modern Europe, and argues, against the conventional wisdom, that China’s historical fertility regime was fairly typical of pre-transition agrarian societies. With Cai Yong, a former CSDE Fellow now at University of North Carolina Population Center, Lavely described and analyzed spatial variation in child sex ratios using 2000 Chinese census data at the county level and GIS techniques. Lavely recently completed a chapter on social values and lifestyles in East Asia for a collection entitled Public Health in East Asia (forthcoming, UC Press).