The DoubleClick Ad Exchange is designed to operate like the New York Stock Exchange, matching buyers and sellers of online ad space in a real-time marketplace. Buyers, in this case ad networks or agency networks, bid on an impression-by-impression basis for inventory that publishers make available. Google will create liquidity in the exchange by linking it to its AdWords ad system and AdSense publisher platform.

The exchange will compete with others. Yahoo purchased Right Media in 2005, which up to now has been the leader among such services. Microsoft bought AdECN in 2007.

Google paints the effort as part of a broader push to reinvigorate display advertising, which has suffered anemic click rates, low prices and high costs for running campaigns.

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