Shortage of Single Ladies Drives Men to Commit

"Women are basically getting snapped up, because the guys want to get her before somebody else does," study author Daniel Kruger, an evolutionary psychologist at the University of Michigan, told LiveScience.

Attack of the single woman

Kruger first became interested in studying the effects of gender imbalance on the marriage market when he caught a glimpse of a magazine cover on a trip to New York City.

"It had this cover picture on it that said, ’Attack of the Single Woman,’ and it had this giant woman with a big red dress like Godzilla tromping through the city," Kruger recalled. "It made me wonder just what would happen to these relationship dynamics if there really was a surplus of single women."

To find out, Kruger analyzed census data on marriage age and gender imbalances in the 50 largest metropolitan areas in America. Using the data, he calculated what's called an operational sex ratio, which is the number of sexually available men per 100 sexually available women, multiplied by 100. A ratio of 100 means a balanced population, while numbers larger than 100 indicate a surplus of men. A ratio of 110, for example, means 11 men are available for every 10 women. A ratio of 90 would mean nine men are available for every 10 women.

After controlling for income and race, Kruger found that in areas where women were scarce, women married slightly earlier. Men's average age of marriage didn’t change relative to the abundance of potential mates, but they did show more variability in the age when they married than women did. That's likely because guys who can snag a women will settle down quickly, Kruger said, but because women can be more choosey, other men may have to build up their finances and social status before they can catch a bride.

"[Some guys will] settle down and take the women before other guys can," Kruger said. "But other guys will have to work more and thus they'll get married at later ages."

Top imbalanced cities

The top five areas where women were scarce, with their gender ratio and median age of marriage for women, were:

• Las Vegas: ratio 116, 24.5 years (Median marriage age for women)
• San Diego: ratio 115, 25.9 years
• Salt Lake City: ratio 113, 23.2 years
• Austin, Texas: ratio 112, 26.2 years
• Phoenix: ratio 111, 25 years

The top five areas where men were scarce were:

• Birmingham, Ala.: ratio 88, 26.7 years (Median marriage age for women)
• Memphis, Tenn.: ratio 88, 27.2 years
• New Orleans: ratio 89, 27.8 years
• Richmond, Va.: ratio 89, 26.3 years
• A three-way tie for New York City, Philadelphia and Washington, D.C., ratio 92, where median marriage ages were 28.3, 27.9 and 27.8, respectively.