Does Amazon's Dual Role Weaken Marketplace Competition?

Amazon's dual role, as both marketplace owner and first-party (1P) seller, gives it power over third-party (3P) sellers who sell similar items. This dual role can weaken 3P sellers’ ability to compete, possibly harming 3P sellers and consumers. We examine three aspects of marketplace competition. First, we examine price change dependencies. We find that 1P prices drop after either Buy Box (i.e., the “Add to Cart” or default sales box on Amazon's product page) prices increase or large 3P price increases occur; 3P prices decrease subsequently. Second, we analyze Buy Box seller selection because this is a critical conduit for demand. We find that both high 1P and 3P prices are penalized in Buy Box selection. Low-reputation and intermittent 3P sellers cannot win the Buy Box even at significantly lower prices. For some prices, the Buy Box favors 1P sellers over equal-priced 3P sellers and vice versa for other prices. Third, to see whether entry barriers weaken competition, we estimate a 3P seller entry model. Higher 1P prices are associated with more 3P sellers, suggesting low entry barriers. Combined, our results suggest that Amazon's dual role does not weaken competition in the marketplace. We discuss implications for marketplace participants, antitrust policy, and research.