Everything in a store influences its shoppers. From display racks to signage to the color of the walls—“every nook and cranny from the farthest reach of the parking lot to the deepest penetration of the store itself” (4)—the details affect shoppers’ decisions. Until recently, though, anthropologists knew more about the markets of New Guinea than they did about shopping in modern industrial societies. The science of shopping had to be invented.

Author Paco Underhill’s market research company, Envirosell, manages “trackers” who are carefully trained to observe surreptitiously roughly 40 variables in shoppers’ traits. Trackers note these behaviors on a “track sheet”; they can observe up to 50 shoppers per day. Video cameras record specific areas of the store to gather data on the effects that particular layouts, signage, and equipment have on, for example, patron walking patterns or worker fatigue.

Trackers work in groups to study visitors at every type of retail establishment and many large public spaces, including concert halls, museums, train stations, and stadiums. Teams of trackers work from offices in New York City, “Mexico City, São Paulo, Milan, Bangalore, Moscow and Tokyo” (7). Envirosell has worked with half of the world’s top-50 merchant companies and one third of the Fortune Top 100 companies.