The notion of distinct social subsets within the borders of one country may seem obvious today. But at the time it gave the lie to an essential premise of marketing and advertising: that Americans were a single people whose demands could easily be served by one set of consumer products. Even those single-variable parameters that had earlier served the limited efforts at more specific targeting were obsolete. “Forget sex. Forget race, national origin, age, household composition, and wealth,” wrote business author Michael Weiss, describing PRIZM. “The characteristic that defines and separates Americans more than any other is the cluster.”

Tim Wu, The Attention Merchants, loc. 605