Matching in Platforms: Mixing 1-1 and 1-to-Many Auction Formats

Many platforms use online auctions to connect one group of participants to another (e.g., Google Search connects web users to businesses that place ads alongside search results, and uses auctions to price and position these ads). In many cases, especially in lead marketing, the same item (i.e., a user) can be "sold" simultaneously to multiple bidders. Auctions under this selling mechanism allow firms to make price bids for both exclusive and/or shared possession of the item. This paper addresses design and computational challenges for designing auctions that mix 1-1 and 1-many matches, and develops a mechanism that satisfies desirable theoretical properties and is relatively easy to implement in practice.