Jack studies the causes, characteristics, and consequences of human migration in and outside of the United States. He is interested in how migration systems, including how these systems are manifested in unique spatial patterns of migration flows among places, and how they interconnect with other systems (economic, environmental, geopolitical, sociocultural, etc.).​ Jack earned his Ph.D. in sociology at the University of Wisconsin-Madison and his master’s degree from the University of Wisconsin-Milwaukee.