Walmart's best selling items before a hurricane are Strawberry Pop-tarts and Beer

Walmart's best selling items before a hurricane are Strawberry Pop-tarts and Beer


Such knowledge, Wal-Mart has learned, is not only power. It is profit, too.

Plenty of retailers collect data about their stores and their shoppers, and many use the information to try to improve sales. Target Stores, for example, introduced a branded Visa card in 2001 and has used it, along with an arsenal of gadgetry, to gather data ever since. But Wal-Mart amasses more data about the products it sells and its shoppers' buying habits than anyone else, so much so that some privacy advocates worry about potential for abuse.

With 3,600 stores in the United States and roughly 100 million customers walking through the doors each week, Wal-Mart has access to information about a broad slice of America -- from individual Social Security and driver's license numbers to geographic proclivities for Mallomars, or lipsticks, or jugs of antifreeze. The data are gathered item by item at the checkout aisle, then recorded, mapped and updated by store, by state, by region.

By its own count, Wal-Mart has 460 terabytes of data stored on Teradata mainframes, made by NCR, at its Bentonville headquarters. To put that in perspective, the Internet has less than half as much data, according to experts.

Information about products, and often about customers, is most often obtained at checkout scanners. Wireless hand-held units, operated by clerks and managers, gather more inventory data. In most cases, such detail is stored for indefinite lengths of time. Sometimes it is divided into categories or mapped across computer models, and it is increasingly being used to answer discount retailing's rabbinical questions, like how many cashiers are needed during certain hours at a particular store.

All of the data are precious to Wal-Mart. The information forms the basis of the sales meetings the company holds every Saturday, and it is shot across desktops throughout its headquarters and into the places where it does business around the world. Wal-Mart shares some information with its suppliers -- a company like Kraft, for example, can tap into a private extranet, called Retail Link, to see how well its products are selling. But for the most part, Wal-Mart hoards its information obsessively.

It also takes pains to keep the information secret. Some of the systems it uses are custom-built and designed by its own employees, the better to keep competitors off the trail. Companies that sell equipment and software to Wal-Mart are bound by nondisclosure agreements. Three years ago, Wal-Mart summarily announced that it would no longer share its sales data with outside companies, like Information Resources Inc. and ACNielsen, which had paid Wal-Mart for the information and then sold it to other retailers.

"When you look at their behavior, you can tell that Wal-Mart considers data to be a top priority," said Christine Overby, a senior analyst for consumer markets at Forrester Research. Over the years, she said, Wal-Mart executives have spent handsomely for their systems, paying $4 billion in 1991 to create Retail Link and signing onto innovations like bar codes and electronic data interchange, a forerunner of the Internet, well ahead of the pack. Wal-Mart is also driving manufacturers to invest in radio frequency identification. By next October, the company will require its biggest suppliers to tag shipments to some of its distribution centers with tiny transmitters that would eventually let Wal-Mart track every item that it sells.

With so much data at Wal-Mart's corporate fingertips, what are the risks to consumers? Most have no clue that their habits are monitored to such an extent. There are no signs -- like the ones for Wal-Mart's anti-shoplifting cameras -- advising customers that information is being collected and stored. And there is no giveback: Wal-Mart doesn't use loyalty cards and rarely offers promotions based on past purchases.