The Social Study is an online data collection infrastructure developed by all Belgian universities. It was designed to promote longitudinal and interdisciplinary survey research in the social and behavioral sciences. The panel consists of approximately 4,000 individuals aged 16 and older living in private households in Belgium. Following similar online probability panels in the Netherlands, Germany and France, TSS offers the research community new opportunities for high-quality survey research in Belgium.

Panel members are recruited based on a two-stage random sample selected from the National Register. First, boroughs are randomly selected, with the number of sample points proportional to population size, and the size of the sample point depending on the expected response rate. Next, individuals are randomly selected from each of the selected municipalities in proportion to population size. The sample is stratified geographically, municipality size, age and gender.

TSS combines sampling based on the population register with a rigorous recruitment strategy consisting of a push-to-web phase and two face-to-face phases. In Phase 1, individuals receive a letter inviting them to complete the recruitment questionnaire online. If individuals do not respond after this invitation and a reminder letter, an interviewer schedules an initial visit for a face-to-face interview as part of Phase 2. After completion of Phases 1 and 2, the third and final phase involves recontacting hard-to-reach individuals. A specialized group of interviewers contacts individuals again and tries to convince them to be part of TSS. Respondents who want to be part of the panel can participate as online or offline panel members.

After initial recruitment, panelists are surveyed six to 10 times a year. Data collection is conducted both online and on paper, for offline panelists. Panelists receive a reward for each completed questionnaire. TSS organizes two core surveys annually to collect basic information from panelists (demographics, socioeconomic status, household, values, leisure time, political behavior and personality traits). In addition, for a fee, researchers can submit a proposal to collect survey or experimental data from the panel. TSS operates according to Open Science principles: after an embargo period, the carefully pseudonymized files become accessible to the full research community.

Additionally, TSS provides the ability to link the collected research data to administrative data through a streamlined application process. BOPP works closely with the Belgian statistical office (Statbel) to offer linkable data packages that combine information from different administrative sources on the following topics: fertility, migration, relationships, labor market, tax and contextual data. Unlike the survey data collected, the administrative data is not freely accessible but only available for the specific research project.