A woman suffering from a headache walks into a drugstore. She faces a shelf of remedies: mostly bottles of branded aspirin, such as Bayer. Next to those colorful, heavily advertised boxes are store-brand packages of generic aspirin. The woman puts the generic into her basket and goes home.

Before she pops the pill, though, she scans her purchase with a handheld wand provided by Nielsen, which collects data about everything she and tens of thousands of other shoppers buy in stores that include drugstores, club stores, grocery stores, and mass merchandisers. And with a little number-crunching, researchers learn that the woman who opts for the generic drug to soothe her headache is more likely to be a pharmacist or medicine knowledgable person compared to the average Wanjiku.

Link