In the first two years, the project I have finished three important papers and two more are nearing completion. All five study key issues in platform-driven marketplaces, algorithms, and consumer behavior. The first paper, “Retailer-led Marketplaces”, examines hybrid marketplaces where platforms act as both retailers and operators, developing a model to analyze interactions with third-party sellers. Findings indicate that marketplace fee regulation could improve welfare, and the paper lays the groundwork for a follow-up study to explore additional factors. The second paper, “Monetizing Steering”, investigates how platforms choose between algorithmic steering and ad auctions to direct consumers. The study reveals that the optimal steering method varies depending on market conditions, offering policy insights on vertical integration and platform competition. The third, "The “Kill Zone”: When a Platform Copies to Eliminate a Potential Threat" built on our earlier work but incorporated some of the novel ideas from FAPoD and tackles key issue of platform conduct with regards to potential rivals. We show how large platforms may eliminate competitors by copying their products at an early stage and thus forcing them to pursue no-threatening postures. Our results have implications for new approaches of competition policy with regards to dominant platforms. Two further studies are progressing toward working paper status. The first, “How to Impress an Algorithm,” explores how sellers attempt to gain algorithmic favor, such as by setting higher off-platform prices or manipulating reviews, showing that platforms may influence these behaviors to align with their own goals. The second project, “Search Model of (Behavioral) Retargeting,” analyzes consumer search behavior and the dual impacts of retargeting ads, finding that this practice may lower prices by fostering competition, though concentration in ad platforms can affect outcomes. These studies provide critical insights into how platform practices shape competition and consumer welfare, paving the way for evidence-based regulatory guidance.