Being surrounded by dudes could hurt more than your dating prospects. Men tend to unconsciously spend more and save less in cities where males outnumber females, reports the Journal of Personality and Social Psychology.

Researchers looked at 120 U.S. cities and found that men have more credit cards and higher debt in areas where there are more men than women.

In a related experiment, researchers showed subjects photos with either an even number of guys and girls, or ones with a skewed gender ratio. “Men normally take R350 in a month rather than R210 today, which is a great return rate. But show them a bunch of pictures with more guys than girls and they’ll take the R210 now,” says lead researcher Vlad Griskevicius, Ph.D., of the University of Minnesota.

“Sex ratio influences behavior unconsciously, where men don’t even realize that the number of men and women are having any effect on their choices,” Griskevicius explains.

Big surprise: It all comes down to sex. When women are in short supply, men face extra competition. We want to get the girl now, before someone else does—which leads us to make more impulsive financial decisions, says Griskevicius.

According to the 2010 U.S. Census the only states with more men than women were west of the Mississippi. The states with the most women were all in the Northeast.

Your solution: Decide how much you can afford to spend before she distracts you. Then walk out the door with only that much cash in you wallet, says Clinton Gudmunson, Ph.D., assistant professor of family studies at Iowa State University.