The Fragile Families and Child Wellbeing Study (FFCWS) is a longitudinal birth cohort study of American families. Core aims of the study are to learn about the capabilities and relationships of unmarried parents and how the families and children fare on various health and social measures over time. The FFCWS uses a stratified random sampling technique and an oversample of non-marital births. Baseline data collection ran from 1998 to 2000, featuring interviews with both biological parents shortly after children's births as well as the collection of medical records. Follow-up interviews were conducted when the children were 1, 3, 5, 9, 15, and 22 years old. In addition to parent interviews, the follow-up waves included in-home assessments, child care or teacher questionnaires, and interviews