What Could Possibly Go Wrong? Insights From Recruiting a Probability Refreshment Sample for the German Internet Panel In-House

The German Internet Panel (GIP) is the longest-running probability-based online panel of the German population. In 2025, the GIP recruited a new refreshment sample (its fourth sample overall) into the panel. Amidst growing concerns about survey cost, this refreshment differed from previous recruitments in two key aspects: The entire recruitment process was largely conducted in-house, forgoing the help of field institutes and other service providers wherever possible, and only two thirds of the invitations were sent out to a traditional population register sample with the remaining third going to a sample obtained from a commercial address database provider to evaluate it as a potential lower-cost alternative.

The talk details the procedure, materials, and timeline for the 2025 GIP recruitment including obstacles we encountered along the way and how they were overcome. It provides an overview of the sampling procedure to researchers interested in working with GIP data and valuable insights about the recruitment of a probability sample and potential pitfalls to anticipate and avoid to those interested in recruiting their own sample. Comparing the address quality, recruitment results, and sample composition between the commercial address database and a register sample, we conclude that it is not a suitable lower-cost alternative to completely replace traditional register samples. Experimentally including a custom-designed QR code in the invitation did not yield any improved recruitment results compared to a regular QR code.

MaRCS is a seminar series jointly organized by the Mannheim Centre for European Social Research (MZES), the University of Mannheim School of Social Sciences, and GESIS – Leibniz Institute for the Social Sciences.