**Design and Sampling Plan** The study design and sampling plan was preregisterd before data collection. **Timeline** The timeline provides an overview of the timing of the longitudinal survey. **Power Analyses** The analyses folder contains the a priori power analyses that were conducted before data collection. **Sampling Strategy** The sampling strategy contains the calculations for the composition of the stratified sample using governmental data from Belgium, Slovenia, and France. **Sample and Compliance** The sample and compliance folder contains the final numbers of participants and attrition rates.