Sorting by Participation: A Field Experiment in a Stem-cell Registry -- by Michael Haylock, Patrick Kampkötter, Mario Macis, Susanne Seitz, Robert Slonim, Daniel Wiesen

We are grateful for valuable comments and suggestions from Hannah Bae, John Cawley, Alex Chan, Glenn W. Harrison, Ludwig Kuntz, John List, Axel Ockenfels, Al Roth, Dirk Sliwka and from seminar and conference participants at AFE/SPI Chicago 2025, ASHEcon 2024, ASSA Philadelphia 2026, BEHnet Workshop Hamburg 2024, the Operations Management Seminar at the University of Cologne, the dggoe Allocation and distribution workshop 2024, the University of Duisburg-Essen, the Erasmus School of Health Policy and Management Rotterdam Seminar, EUHEA 2024, the Field Experiments in Economics and Business Conference in Heilbronn 2024, the Monash University Centre for Health Economics Seminar, and the University of Passau. We thank Bernd Weinel (CFO), Thilo Mengling (Director Global Medical Science and Political Affairs), Jan Markert (Head of HLA Services), and Juergen Sauter (Head of Scientific Projects), all at DKMS Group gGmbH, as well as Alexander Schmidt (COO, DKMS Registry gGmbH), for their support and invaluable input from a registry management perspective. Susanne Seitz was em- ployed by DKMS Germany at the time of the study. All authors declare no conflict of interest. DKMS reviewed the manuscript for factual accuracy and confidentiality before circulation; the authors retain full responsibility for its content and conclusions. IRB approval was obtained from the Homewood Institutional Review Board, Johns Hopkins University (IRB approval Number HIRB00013790), and from the Ethics Committee of the Faculty of Economics and Social Sciences, University of Tuebingen (IRB approval number A2.5.4-186 ns). Haylock thanks the Deutsche Forschungsgemeinschaft (DFG) for funding under project 566667001. The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Research.

• online appendix
• randomized controlled trials registry entry