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When more women are in the environment, men tend to spend less.

When women are scarce — or, at least, scarcer than men — the men tend to become more financially impulsive, saving less and borrowing more.

And women tend to expect men to spend more, too — on them.

Those findings are from an interesting new study conducted by researchers at several universities, including the University of Minnesota's Carlson School of Management.

The study, which appears in the January issue of the Journal of Personality and Social Psychology, is actually a series of four smaller studies. For the first study, the researchers looked at how the sex ratios in 134 U.S. cities related to two measures of economic impulsivity: credit-card ownership and willingness to borrow money.

(Minneapolis, by the way, was one of those cities. It has 111.4 men for every 100 women.)

"We found that in the cities in which there were more men than women, people tended to have more credit cards and more debt," said Vladas Griskevicius, the study's lead author and an assistant professor of marketing at the Carlson School, in a phone interviewer earlier this week.

Vladas Griskevicius

Take the two Georgia cities of Macon and Columbus, which are located less than 100 miles from each other. In Macon, there are fewer men than women (0.78 single men for every woman), while in Columbus there are fewer women than men (1.18 single men for every woman).

When the researchers looked at the average per-person consumer debt of both cities, they found that the debt of individuals living in Columbus is a remarkable 2.7 standard deviations higher than that of people living in Macon — a difference of $3,479 per person.

Men and money
To test this finding in a more controlled environment, Griskevicius and his colleagues had 205 men and women, aged 18 to 36, look at photos that had either more men, more women, or were neutral. They paid the volunteers $10 and then asked them to choose between receiving a second payment the next day or a significantly larger amount of money in one month.

After analyzing the volunteers' choices, the researchers discovered an intriguing trend. "When there were more women in the photos, men tended to opt to get the money later so they could get the greater rate of return," said Griskevicius. "However, when there were more men than women in the photos, men took the money right away. They acted more impulsively."

To determine if those results reflected a real effect, the researchers designed another study. Instead of having volunteers look at photos, the researchers had them read news articles that had been doctored to make it seem as if there were either more women or more men living in the volunteers' local area. Then they asked the volunteers how much money they would like to save from a paycheck each month — and how much money they'd like to borrow from a credit card for immediate expenses.

Once again, the men acted more financially impulsive when they perceived their environment had more men than women. In that situation, their willingness to save dropped by 42 percent and their willingness to borrow increased by 84 percent.

Women affected, too
But what about the women who participated in the studies? They didn't change their financial habits in reaction to different sex ratios, said Griskevicius, but they did alter how they thought men should spend their money. A fourth study found that when women perceived that they were in an environment in which other females were scarce, they expected men to spend more money on traditional mating-related behaviors, such as a Valentine's Day gift, a romantic dinner and an engagement ring.

"What's interesting about these studies is that all these effects are happening subconsciously," said Griskevicius. "Women aren't actually calculating these things out deliberately. They're just reading a story or looking at some photos and then they just feel differently. They feel like men should pay more money."

Other cultures
The volunteers in this study were all Americans, but Griskevicius believes sex ratios probably affect financial behavior in other countries as well, although perhaps in different ways. In China, for example, men have been found to save rather than spend more money when in an environment that has more men.

"This appears initially to be kind of weird," said Griskevicius. "But in China you have a long history of bride price, where the groom's family pays the bride's family." So, whereas in the U.S., men might spend extravagantly to court a woman when women are scarce, in China, they appear to save extravagantly.

An unconscious influence
The effects of sex ratios on our economic decisions (like their effects on other behaviors, such as aggression) are entirely unconscious, Griskevicius stressed.

"What our study shows is that things that are in our environment — like the ratio of men to women who are standing around you when you're in the check-out aisle at the grocery store, for instance — can change how you make financial decisions," he said. "It can change whether you decide to make an impulse purchase or keep your money in your wallet."

"You could overcome this by being consciously aware of it," Griskevicius added. "You could say, ‘Hey, wait a second. My behavior is being influenced by these environmental factors.' But the truth of the matter is, people rarely do that. We're just too busy with our daily lives to always remind ourselves that our environment is influencing our behavior."

Griskevicius said he and his colleagues are currently studying how sex ratio influences women's career choices. "We're looking at whether a scarcity of men is more likely to lead women to choose briefcase over baby," he said. "A lack of men might lead women to pursue high-investment careers, careers that take a lot of time, but often lead women to have kids much later or to not have kids at all."

That study is scheduled to be completed later this year.