Dr. Rebecca L. Clark is Chief of the Population Dynamics Branch (PDB) at the NICHD. PDB supports research and research training in demography; behavioral and social science research on reproductive health; and population health—human health, productivity, behavior, and development at the population level. Dr. Clark is currently serving as a member of the Board of Directors of the Population Association of America (PAA) and has held similar positions for the Southern Demographic Association and the Sociology of Population Section of the American Sociological Association. Dr. Clark received her Ph.D. in sociology with specializations in demography and urban studies from Brown University. In 1990, she received the Dorothy S. Thomas Award from the PAA. Before coming to NICHD, Dr. Clark was a senior researcher at The Urban Institute, specializing in research on immigration and immigrants.