When you hit the checkout line at your local supermarket and give the cashier your phone number or loyalty card, you are handing over a valuable treasure trove of data that may not be limited to the items in your shopping cart. Many grocers systematically infer information about you from your purchases and “enrich” the personal information you provide with additional data from third-party brokers, potentially including your race, ethnicity, age, finances, employment, and online activities. Some of them even track your precise movements in stores. They then analyze all this data about you and sell it to consumer brands eager to use it to precisely target you with advertising and otherwise improve their sales efforts.

Keegan, J. (2023, February 16). Forget milk and eggs: Supermarkets are having a fire sale on data about you. The Markup. https://themarkup.org/privacy/2023/02/16/forget-milk-and-eggs-supermarkets-are-having-a-fire-sale-on-data-about-you