These data were collected by Jere R. Behrman, Mark R. Rosenzweig, and Paul Taubman of the Economics Department at the University of Pennsylvania with funds from the National Center on the Educational Quality of the Workforce, the Economics Institute Research Fund, the Boettner Research Fund, the Population Study Center NIA Supplement, and the University Research Foundation -- all of the University of Pennsylvania. The survey instrument was designed in collaboration with the Temple University Institute of Survey Research. The data were collected, under the leadership of David T. Lykken, then Director of the Minnesota Twin/Family Registry (MTR), by the staff of the MTR. Users of the data should acknowledge the source. The MTR is the largest birth-record-based twins registry in the United States, assembled between 1983 and 1990 starting with birth records on all twins (both monozygotic, MZ, and dizygotic, DZ) born in Minnesota in 1936-55. Details of the sample and its characteristics are in Lykken, D. T., T. J. Bouchard, M. McGue, and A. Tellegen, 1990, "The Minnesota Twin Family Registry: Some Initial Findings," Acta Genet Med Gemellol 39, 35-70. The survey instrument was mailed out starting in May 1994 to the 6638 members of same-sex pairs who had filled out an earlier instrument sent to them by the MTR and for whom the MTR had current addresses. 3682 twins returned a completed questionnaire, including both responses from both members of some pairs and only one member of others.
To access the data please follow the instructions in the Application.
The codebook provides the original questionnaire, each response to which includes the alphabetic code by which each data entry can be found for that question in the STATA data files. Each observation is identified by ID and a one-digit SIB code (to identify the two sibs in a twinship). Zyg1.dta gives the zygosity code (1 = MZ, 2= DZ), gender, and birth year. The data are presented in exactly the form that the respondents provided the data in order to give users the maximum flexibility in constructing variables that they desire. X is used to indicate a blank response. To protect the confidentiality of the twins, identifying information relating to location, names of schools, and names of people is not included in these public use data. Click Here to view the Codebook in .pdf format.