Relevance & Research Question
RDS is a network sampling technique for surveying complex populations in the absence of sampling frames. The idea is simple: identify some people (“seeds”) who belong or have access to the target population, encourage them to start a survey invitation chain-referral process in their community, ensure that every respondent can be traced back along the referral chain. But who will recruit? And whom? And which strategies help initiate the referral process?
Methods & Data
We conducted a pilot study in 2023 where we invited 5,000 panel study members to a multi-topic online survey. During the survey, we asked respondents whether they would be willing to recruit up to three of their network members. If they agreed, we asked them about their relationship with those network members as well as these people’s ages, gender, and education and provided unique survey invitation links to be shared virtually. As part of the study, we experimentally varied the RDS consent wording, information layout, and survey link sharing options. We also applied a dual incentive scheme, rewarding seeds as well as recruits.
Results
Overall, 624 initial respondents (27%) were willing to invite network members. They recruited 782 people (i.e., on average 1.25 people per seed). Recruits were mostly invited via email (46%) or WhatsApp (43%) and belonged to the seeds’ family (53%) and friends (38%). Only 20% of recruits are in contact with the seed less than once a week, suggesting recruitment mostly among close ties. We find an adequate gender balance (52% female) and representation of people with migration background (22%) in our data, but a high share of people with college or university degrees (52%) and high median age (52 years). The impact of the experimental design on recruitment success is negligible.
Added Value
While in theory, RDS is a promising procedure, it often fails in practice. Among other challenges, this is commonly due to the fact that seeds will not or only insufficiently start the chain-referral process. Our project shows in which target groups initiating RDS may work and to what extent UX enhancements may increase RDS success.