Google Begins Tracking Credit Card Spending in Physical Retail Stores

Google has begun using billions of credit-card transaction records to prove that its online ads are promting people to make purchases-even when they happen offline in brick-and-morter stores, the company said Tuesday. 

The advance allows Google to determine how many sales have been generated by digital ad campaign a goal that industry insiders have long described as "the holy grail" of online advertising. But the announcement also renewed long-standing privacy complaints about how the company uses personal information.

To power its multibillion-dollar advertising juggernaut, Google already analyses users' Web browsing, search history and geographic locations, using data from popular Google-owened apps such as YouTube, Gmail, Google Maps nd the Google Play store. All that information is tied to the real identities of users when they log into Google's services.

Privacy advocates said few people understand that thier purchases are bieng analysed in this way and could feel uneasy, despite assurances from Google that it has taken steps to protect the personal information of its users.