Several years ago, managers of the American store Walmart discovered some surprising information from their sales records. They found that when customers bought diapers, they often bought beer at the same time. This was because American housewives with newborn babies often called their husbands at work and had them buy diapers； they often picked up some beer as well. After discovering this, Walmart rearranged its stores. It placed diapers and beer closer together. Soon afterward, sales of both items began to increase. 

      This is just one successful example of how stores improve sales by analyzing consumer behavior. They study their computerized inventory records to find out what products people buy most often or when they buy certain products. Sales records can also be used in conjunction with other types of research, such as market surveys or psychological studies. For instance, many stores take psychology into consideration when they decide where to place special sale items. The best location is often near the middle or rear of the store, rather than right up in front. This way, as customers look for the sale item, they will have to pass by many other products, some of which will end up in their carts.

       Psychologists have also found that customers buy more when they hear certain types of music in a store. In addition, they know that customers tend to make last-minute decisions just before they pay for their purchases. This is why stores place small, inexpensive items such as candy or batteries close to the cash register. Magazines are also frequently placed in the same place； as waiting to pay, people may flip through a magazine and then decide to buy it. 

      Studies of consumer behavior can be expensive and time-consuming. It is only large department stores or chain stores that can afford them. But even small shops can benefit if they simply pay attention to the buying habits of their customers. And, of course, customers can also benefit if they understand their own buying behavior. With the knowledge, they can avoid spending more than they originally plan to.