The TwinLife study covers in its first wave about 4000 same-sex twin pairs in Germany of whom both biological and social parents plus – if existing – one sibling and partners are surveyed for 10 years. The sample selection was conducted by the social research institute Kantar Public (formerly infratest). Alternating from year to year, face-to-face interviews with psychological tests and shorter telephone interviews are conducted. In a cross-sequential design over 10 years, the study covers the age range from early childhood (five years) to adulthood (31 years) with extensive measurements of individual life courses and developmental trajectories in the domains of physical and psychological health, skill formation and education, career and labor market attainment, social integration and participation, subjective perception of quality of life, and deviant behavior and behavioral problems combined with detailed reports about the social environment (Hahn et al. 2016).
The net sample of the TwinLife Survey of the preschool cohort amounts to 2,020 twins in 1,016 households. Starting from a gross sample of 5,472 twins in 2,736 households, this equates to a response rate of about 37 percent.
Parents were willing to reveal the address for 838 ECEC institutions. After correcting for duplicates and deleting addresses of schools and child minders, this translates to 760 unique center addresses included in the subsequent Institution survey.
Out of these 760 unique ECEC institutions, 485 (63.8 percent) participated in the Institution Survey.
Case numbers and response rates from Institution Survey
Hahn, E., Gottschling, J., Bleidorn, W., Kandler, C., Spengler, M., Kornadt, A., Schulz, W., Schunck, R., Baier, T., Krell, K., Lang, V., Lenau, F., Peters, A.-L., Diewald, M., Riemann, R., & Spinath, F.M. (2016). What Drives the Development of Social Inequality Over the Life Course? The German TwinLife Study. Twin Research and Human Genetics, 19(6), 659-672.
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