Internal competition may motivate worker effort, yet the benefits of competition may depend critically on workers’ relative abilities: large skill differences may reduce efforts. I use panel data from professional golf tournaments and find that the presence of a superstar is associated with...

Theory models of platform competition predict that prices and buyer-seller ratios should be approximately equal on coexisting auction sites. Using field experiments on eBay and Yahoo Auctions, we find evidence that is inconsistent with equilibrium hypotheses and suggest that the market is...