1 | 21 Synthesis year file (70,631 person-years in total). For the investigation of the impact of major life events on the likelihood of stopping a sport during the transition to adulthood (Chapter 3), I narrowed down the person-period file and created person-year records extending from the age of 18 up to and including age 35 or the age upon the interview when respondents were younger than 35 years at that time. The risk set used for the analysis of stopping participation in a sport in general consisted of 24,947 person-years in which 2272 respondents were at risk of stopping a sport, because they were practising at least one sport (regardless of the context). The risk set used for the analysis of ending a sport club membership is a subset of the risk set for stopping a sport, consisting of 13,955 person-years in which 1530 respondents were at risk of ending sport club membership, because they were practising one or more sports in a club context. In Chapter 4, I employ data from the 2009 and 2013 waves of the Netherlands Longitudinal Lifecourse Study (NELLS; Tolsma et al., 2014). This is a nationally representative large-scale panel survey of 15–45 year olds in the Netherlands. The fieldwork of the first wave has been done by Intomart GfK. The questionnaire of the first wave consisted of two parts: a face-to-face fully structured interview and a self-completion questionnaire. The fieldwork of the second wave has been done by Veldkamp in a mixed mode: all questions were either administered face-to-face or via a computer assisted web interview (CAWI). To facilitate the study of social dynamics from a life-course perspective, data was collected on a range of topics, like respondents’ life transitions and leisure activities, including sport. This makes NELLS especially suited for my investigation of changes in sport participation and the influences of life events that mark the transition to adulthood. I used information of the respondents who participated in both waves, resulting in a sample of 2317 respondents for the analyses of the number of sports and sport frequency. For the analysis of the likelihood to switch from a club setting to a “lighter” setting or not practising sport at all, I restricted the sample to the 522 individuals who practised sport (mostly) in a club setting in the first wave. In Chapter 5, I draw from primary narrative information from 46 Dutch adults, gathered in two rounds of interviews. In a first round, narrative interviews were held with 19 adults (10 women and 9 men) aged between 29 and 77. To reach saturation of the information with respect to sport participation and life events related to the transition to adulthood in particular, more data on this phase was obtained in a second round of interviews with 17 mothers and 10