He works on methods to study issues involving social inequality, the epidemic spread of disease, and collective behavior.

His paternal 4th great-grandfather is Thomas Hannan, a revolutionary war soldier and the first Anglo settler of the Kanawha River region of Virginia (now West Virginia)[7] His cousin, Kathie Stewart, is a founding member of the Cleveland Baroque Orchestra (principal flutist), and curator of historical keyboards (e.g., harpsichords) for the Oberlin Conservatory of Music.

[8] During his time as a student at Chicago, he was a research assistant for the National Social Life, Health, and Aging Project, on which he eventually became a co-investigator.

[10] One of his most important papers, co-authored with Kim Weeden, used data on the networks of students on college campuses to demonstrate that the risk of the epidemic spread of SARS-CoV-2 could be curbed by shutting down particularly large classes and moving them online.

He has applied sequence analysis to the study of individuals' time-use patterns, which have revealed important gender differences in time allocation, among other topics, with collaborators Jonathan Gershuny (CBE) and Oriel Sullivan.