Mechanism choice and the buy-it-now auction: A structural model of competing buyers and sellers

•This paper studies sales mechanisms on online sales platforms like eBay.•The model incorporates competition between buyers as well as between sellers.•It is estimated using data from sales of baseball tickets on eBay.•I investigate how the existence of buy-it-now auctions changes welfare.•Buyers are better off and sellers are worse off when buy-it-now auctions exist.

A striking feature of many online sales platforms is the coexistence of multiple sales mechanisms. Items on eBay, for instance, are frequently offered through auctions, posted prices, and buy-it-now auctions. In this article, I study how this mechanism multiplicity influences the welfare of buyers and sellers. I specify and estimate a structural model of mechanism choice in online markets, in which I consider both sides of the market: On the demand side, buyers' choices among available listings are equilibrium outcomes of an entry game. On the supply side, sellers make equilibrium decisions when choosing sales mechanisms and prices. I estimate this model using data from sales of baseball tickets on eBay and calculate consumer and seller rents in three markets: the actual market with all three sales mechanisms and two counterfactual markets with auctions and fixed prices or only fixed-price listings, respectively. I find that the addition of auctions to fixed-price markets hurts sellers and risk-averse buyers but benefits risk-neutral buyers. Additionally, the consumer surplus increases when buy-it-now auctions are offered but the seller surplus is reduced further. I discuss the intuition for the cause of this result.