Economists at eBay use the empirical and theoretical tools of economics to expand the frontiers of e-commerce research. Our work explores the interacting incentives of buyers and sellers, emphasizing causal relationships between actions and outcomes, and the potential sources of marketplace frictions. We aspire to address some of the most challenging questions about markets through rigorous and original research on the rich data from eBay’s robust marketplace, and to use these insights to shape its growth. This research spans a broad range of topics, including trust, reputation, marketing effectiveness, bargaining, consumer search, and international trade. The economics group works closely with other academics from Stanford, Columbia, the University of Chicago, UC Berkeley and other top universities on collaborative research projects. Our work also brings us across disciplinary lines and across different eBay teams in areas like search, machine learning, and natural language processing, because we are leveraging tools that push the envelope of economics.