Gannett also claims Google controls the ad exchange market, which organizes real-time auctions among potential buyers for ad space. While Google's exchange controls more than 60 percent of the market, competitors have shares in the single digits, the suit says. Gannett alleges that Google largely bars buyers using its exchange from participating in any others. By tying its services together, Google has effectively ensured that publishers have to go through the company to reach the majority of buyers, according to the complaint.