Duncan spent the first 25 years of my career at the University of Michigan working on and ultimately directing the Panel Study of Income Dynamics (PSID) data collection project. Since 1968, the PSID has collected economic, demographic, health, behavior and attainment data from a representative sample of U.S. individuals and the households in which they reside. With these and other data he studied the economic mobility of the U.S. population, both within and across generations, with a particular focus on low-income families.