**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.