16.8 Linking data
We now have two sets of data held by the supermarket: the data about its own products and the personal data about customers. Individually, each of these two sets of information has important uses. However, when they are linked, they provide a very powerful tool for the supermarket.
The personal data from a loyalty card scheme can be used to compile targeted mailing lists, because data about your purchases can help build up a profile of how you spend your money. For example, the supermarket knows from data held about your spending patterns whether you buy products for babies, children or pets, and whether you prefer particular brands. This information allows the supermarket to send you appropriate information and special offers.
The mailing lists that supermarkets gather from loyalty card schemes may also be sold to other businesses. However, in the UK the Data Protection Act (1998) applies to the personal data gathered by loyalty card schemes, which means that customers must be asked for permission to use information about them.