His research focuses on the comparative examination of social inequality, especially with respect to race and ethnicity, in global perspective. This research uses both quantitative and qualitative methods, while drawing heavily upon contemporary theories of social cognition and categories. By deeply engaging with issues of measurement and methodology, it examines the complex relationships between social categories and social inequality; and extends into topics such as social demography, health, aging, social psychology, sociology of the body, political sociology, and comparative/historical sociology.