Google allegedly purchases data from Mastercard pertaining to the purchase history of its 2 billion cardholders. They then cross-referenced it with Google's own online advertising tracking to learn how Mastercard cardholders viewed and reacted to, online advertising from Google in relation to physical store sales. Google boasts of its "Store Sales Measurement," and access to "approximately 70 percent" of U.S. credit and debit cards through partners. Through this test program, Google can anonymously match these existing user profiles to purchases made in physical stores. The result is powerful: Google knows that people clicked on ads and can now tell advertisers that this activity led to actual store sales. Since 2014, Google has flagged for advertisers when someone who clicked an ad visits a physical store, using the Location History feature in Google Maps.