How much does your supermarket know about you? Retailers are building an ecosystem of data' using loyalty cards and are making millions from mining the information, insiders reveal

Supermarkets have built an 'ecosystem of data' from shoppers using loyalty cards as they make millions by 'relentlessly mining' information, insiders have revealed. Data science analysts go through purchases every day from Tesco and Sainsbury's customers who use their Clubcard or Nectar cards to benefit from lower prices. Presenter Alexis Conran then said to him: 'So essentially, what you're telling me, if I've understood you correctly, the reason that Tesco and Sainsbury's and every other retailer wants you, the customer, to become part of a loyalty scheme is because by doing so I'm opening up a big and rather profitable source of income for the retailer, which is I'm giving them my data and they're going to make money off that.' A company called Dunnhumby, owned by Tesco, analyses data from Clubcard spending The Competition and Markets Authority said the increase in some supermarkets making cheaper prices only available for loyalty card members had led to it examining the practice as part of its work to help tackle cost-of-living pressures in the groceries sector. In April last year, Sainsbury's introduced lower prices on hundreds of products in supermarkets and online for members of its loyalty card Nectar.