Evan Hughes summarizes the theory of "sexual economics" in Premarital Sex in America by Mark Regnerus and Jeremy Uecker:

The rise of “the hookup culture” at colleges, they argue, can be attributed in part to the increasing scarcity of men on campusan oversupply of sellers works to a buyer’s advantage. Sexual economics also suggests that many women look unkindly on promiscuous members of the same sex out of the same impulse that makes retailers angry when Wal-Mart comes to town: they are being undersold, and now they have to give discounts or lose customers.

Hughes isn't buying it:

Equating an intimate act to a business transaction is not only crass and reductive; it is also analytically misleading. The analogy to commerce implies an adversarial situation wherein the buyer always wants to pay the minimum and the seller wants to get the maximum. But men often find themselves bestowing attention, falling in love, and getting married after they have already been sleeping with the woman in question. Sexual economics has trouble accounting for that. Men willingly overspend, which describes approximately no one who buys a car. Similarly, the pay-for-play hypothesis fails to capture the fact that most women do not want to extract caring and love from a person disinclined to offer it, and they do not see sex as something they wish they could avoid until marriage.

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