They have two main reasons, but it depends a lot on the natureof the business.'One is to assess their sales by products, areas , customers'tastes and the like. This helps them plan ahead, especially if achain wanting to establish a branch in a given area.'The other, if they use on-line or text-message advertising, ismore intrusive, and that is to direct advertising to you that ismore closely aligned to what they think you will want. You may havenoticed on some social sites, adverts that seems to know where,approximately, you live. It's a bit creepy but can beunintentionally amusing.'Their methods vary but the big supermarket chains use theirso-called "loyalty cards" and your credit-card transactions forthis research.