The authors are grateful to the department editor, the associate editor, and three anonymous reviewers for their many sharp comments and constructive suggestions that significantly improved the paper, both in content and exposition. The authors thank seminar attendees at the University of Texas at Dallas, the University of Virginia, the University of Cologne, Cornell University, and Dartmouth College; and conference participants at the 2023 Manufacturing & Service Operations Management Conference at McGill University, the 2023 Behavioral Operations Management Conference at Johns Hopkins University, the 2023 Asia-Pacific Economic Science Association Meeting (online), the 2023 European Workshop on Market Design (in Mannheim, Germany), the 2023 Universidad Torcuato Di Tella Workshop in Operations, Networks & Data Analytics (in Argentina), the 2023 INFORMS Annual Meeting (in Phoenix), and the 2022 INFORMS Annual Meeting (in Indianapolis) for helpful comments. The authors also thank Max Grossmann for his generous support for the z-Tree Unleashed system.