Digital platforms have fundamentally changed how consumers search for, evaluate, and purchase products. Through design mechanisms such as rankings, recommendations, and information provision, platforms actively shape consumer decision making and market outcomes. As digital platforms continue to gain economic importance, understanding the behavioral consequences of platform design has become increasingly relevant for researchers, managers, and policymakers. While prior research has generated valuable insights into individual platform design mechanisms, existing studies have largely examined these mechanisms in isolation, leaving a fragmented understanding of how platform design shapes consumer behavior and market outcomes across digital marketplaces. Addressing this fragmentation, this cumulative dissertation adopts an integrative perspective on platform design. It examines how platform-controlled design mechanisms influence consumer behavior throughout the consumer decision-making process in digital marketplaces. The empirical studies investigate how platform endorsement badges influence consumer search and purchase behavior in online retail environments and how standardized privacy disclosures affect consumer engagement in mobile app marketplaces. Complementing these empirical findings, the third article synthesizes the literature on self-preferencing by digital platforms, reviewing current evidence on its consequences, prevalence, and regulation. To provide robust evidence across these settings, the dissertation combines a large-scale audit study, a browser-based lab-in-the-field experiment, consumer surveys, quasi-experimental analyses, and a systematic literature review. Collectively, the findings in this cumulative dissertation provide implications for third-party sellers and platform operators while informing current discussions on platform governance and regulation.
