Spent is about “display” consumerism. It leaves aside strictly utilitarian purchases like baloney or tampons. Understanding display consumerism, according to Miller, requires adding one part Thorstein Veblen to one part Darwin. From Veblen’s classic Theory of the Leisure Class (1899), Miller appropriates the concept of “conspicuous consumption,” whereby people live and spend wastefully just to flaunt the fact that they can. From Darwin, Miller appropriates sexual selection theory—“costly signaling theory” in modern parlance—whereby animals compete by sending signals of their underlying genetic quality. As with the gaudy displays of peacocks, purchasing decisions frequently represent attempts to advertise “fundamental biological virtues” like “bodily traits of health, fitness, fertility, youth, and attractiveness, and mental traits of intelligence and personality.” Why spend $160,000 on a prestigious university degree? To make a “narcissistic self-display” of one’s intelligence and diligence. Why stuff yourself into a push-up bra and smear pigment across your lips and cheekbones? To try to enhance—or fake—your fertility signals.