If a user also provides their email address to a local store, to sign up for a loyalty program, for example, Yahoo can match the user to the purchase and figure out how many people who clicked on an online ad went to on to make a purchase at their local store. That's how it performed the hyperlocal study.
As with all services that track user behavior closely, Yahoo will have to be careful not to stir up privacy concerns. Raghavan said Yahoo employed an outside company to match the ad clicks with the purchase data, so Yahoo and the advertisers received aggregate data and not people's individual purchase history.
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