(MONEY Magazine) – The prejudice is at least as old as Henry VIII, and not the women's movement, the WNBA or even Condoleezza Rice has been able to dispel it. Surveys have shown that while American women are just as happy to have girl babies as boys, American fathers stubbornly prefer sons to daughters by a margin of more than two to one. A new study by economists Gordon Dahl of the University of Rochester and Enrico Moretti of UCLA shows how deeply this preference colors decisions that families make about their lives and money.

According to data Moretti and Dahl culled from hospitals, birth certificates and census records, parents with girls only were more likely to be divorced, and divorced dads were more likely to have custody of their sons than of their daughters. In the case of "shotgun marriages," the economists found, men were far more likely to marry the mother of their child when ultrasound revealed that the baby was a boy. Moretti and Dahl also say some Americans are so set on a boy that they just keep on having kids—and ringing up all the expenses that come with them—until a son finally arrives.

The desire for sons is less intense in the U.S. than elsewhere, particularly in China and Vietnam, they say. But the economists also speculate that as medical technology makes it easier to choose a baby's sex, "the sex ratio in the population may slowly become more male." —DAVID FUTRELLE