Google is introducing a new advertising solution that can track how well online ads translate to offline purchases, a move that helps advertisers gauge the effectiveness of their digital campaigns while leaving users concerned about their privacy on the web.

The US internet giant unveiled a new ad management system called Google Attribution and a store sales measuring tool that links online ads to offline store sales based on user email accounts and credit card transaction records, at the Google Marketing Next Month conference in San Francisco this week, according to media reports Wednesday.

Though the tech giant has long used its vast pool of accumulated user data to determine when they click on ads and make purchases, linking users’ online activities with offline spending is seen to further extend the scope of the tech giant’s analytic power.

Google Attribution works by measuring a user’s online activity via AdWords, Google Analytics and DoubleClick Search, making it easy to pool data from various marketing channels and gain a “complete view of your performance,” Google said in a blog post.

In addition, Google will introduce in the coming months the “store sales measurement,” currently available as a beta service, that “measures in-store revenue in addition to the store visits delivered by your Search and Shopping ads.”

Essentially, companies that collect email addresses from customers when they make a purchase can import their store transactions into Google’s AdWords system to compare which items customers purchase against advertisement spend.

Firms can also extrapolate such user purchase data by using credit and debit card transaction records to be provided by third-party companies, Google said.

In doing so, the new ad management solution aims to answer the question: “Is my marketing working?” and “makes it possible for every marketer to measure the impact of their marketing across devices and channels,” Google said.

The move has sparked criticism from privacy advocates, such as the US-based Electronic Privacy Information Center, that have taken issue with how Google handles and makes use of personal information.

By using users’ credit card records to connect their digital trails to purchases made in the real world, Google is analyzing people’s activities in a way that many could perceive as overly intrusive, they argue.

“What we have learned is that it’s extremely difficult to anonymize data,” Paul Stephens of US-based consumer advocacy group Privacy Rights Clearinghouse told the Washington Post. “If you care about your privacy, you definitely need to be concerned,” he said.

Google has asserted that it has “custom encryption technology” to ensure that user data remains anonymous, private and secure, though it does not reveal in detail how it safeguards the identities of users.

By Sohn Ji-young (jys@heraldcorp.com)