This push pertains to a topic that in other realms is far more controversial: Policy experts, privacy advocates, corporate executives, and academics are arguing fiercely about the legality and ethics of data mining by online advertisers and the government. Meanwhile, retailers are doing the same thing and attracting comparatively little attention. As they continue, they are quietly sending consumers the message that offering up information about themselves is simply a prerequisite in a new era of shopping.

Even if retailers frame their increasing reliance on analytics as the natural next step of a competitive industry, there’s no law of shopping stating that sellers will treat customers better and better the more they learn about them. In fact, the fallacy of expecting that to happen becomes clear when examining how the act of buying things has changed in the past 250-plus years. Shoppers are entering a third stage of American retailing, one that has more in common with the 18th and 19th centuries than with the one that just passed.

The first stage was that of the peddler and small merchant. European sellers of the 1700s, for example, followed well-worn strategies to maximize their returns on goods. To remember what they paid their suppliers, peddlers marked the back or bottom of their products with symbols known only to them or close relations. In addition to keeping track of the prices and loans they negotiated, they kept track of their customers: They recorded people’s occupations, their spouse’s names, their family connections, and their social standing in their village. These records allowed peddlers to customize their sales pitches. Their “preferred” customers were getting especially good deals, the merchants could say, while keeping secret that those buyers were actually paying more than other groups.

As many European immigrants poured into North America during the 18th and 19th centuries, the peddling business migrated with them. When these salesmen were able to amass a bit of cash, some established small general stores or food markets. Settling down allowed merchants to develop more-personal relationships with their customers than they could going door-to-door or marketplace-to-marketplace. Yet personalized deals increasingly caused angst for shopkeepers, perhaps more than when they were itinerants. Customers suspected that grocers of ethnicities different from their own overcharged them or supplied them with lower-quality products. Many black people who frequented stores owned by whites were especially suspicious about this opacity of price and quality.

During the mid- and late 19th century, these strains helped produce America’s second stage of retailing: the era of posted prices. Although Quaker merchants had long believed it morally abhorrent to charge different people different amounts for the same items, a growing number of non-Quaker merchants began to adopt fixed prices because doing so saved them the trouble of teaching their clerks how to bargain—an important consideration during the growth, beginning in the 1840s, of multi-story, multi-department emporia with many employees (such as A.T. Stewart, Lord and Taylor, and Wannamaker).