The authors wish to thank Linda Piccinino at the National Center for Health Statistics for assistance with accessing confidential data, Jennifer Garner for excellent research assistance, and Jeffrey Zax for helpful comments on an earlier draft.
The National Survey of Family Growth collected extremely sensitive information from its respondents. To ensure that the identity of these respondents is kept secret, no information with regard to state or county of residence is available to researchers. However, a large number of tract-, county-, and state-level variables are present in the data, and with the help of Linda Piccinino at the NCHS we were able to incorporate additional information. The original sources of these variables are the Alan Guttmacher Institute; the Bureau of Health Professionals, Office of Data Analysis and Management; the Centers for Disease Control and Prevention; J. F. Mertz, C. A. Jackson, and J. A. Klerman; T. N. Steinberg; and the US Bureau of the Census.