Constance L. Hays takes a look at Wal-Marts massive customer/product database.

URRICANE FRANCES was on its way, barreling across the Caribbean, threatening a direct hit on Florida’s Atlantic coast. Residents made for higher ground, but far away, in Bentonville, Ark., executives at Wal-Mart Stores decided that the situation offered a great opportunity for one of their newest data-driven weapons, something that the company calls predictive technology.
A week ahead of the storm’s landfall, Linda M. Dillman, Wal-Mart’s chief information officer, pressed her staff to come up with forecasts based on what had happened when Hurricane Charley struck several weeks earlier. Backed by the trillions of bytes’ worth of shopper history that is stored in Wal-Mart’s computer network, she felt that the company could “start predicting what’s going to happen, instead of waiting for it to happen,” as she put it.
The experts mined the data and found that the stores would indeed need certain products – and not just the usual flashlights. “We didn’t know in the past that strawberry Pop-Tarts increase in sales, like seven times their normal sales rate, ahead of a hurricane,” Ms. Dillman said in a recent interview. “And the pre-hurricane top-selling item was beer.”