According to the study, which examined 18- to 28-year-old married and co-habitating respondents who were in the same relationship for more than a year, men who were completely dependent on their female partner's income were five times more likely to cheat than men who contributed an equal amount of money to the partnership. The relationship between economic dependence and infidelity disappeared when age, education level, income, religious attendance, and relationship satisfaction were taken into account.
What was the ideal ratio? Men were the least likely to cheat when their partners made approximately 75% of their incomes, about the amount that women earn in relation to men in the work force historically.
"One or more of these variables is impacting the relationship," said Christin Munsch, a sociology Ph.D. candidate at Cornell University, and author of the study, 'The Effect of Relative Income Disparity on Infidelity for Men and Women'. "For example, it may be that men who make less money than their partners are more unhappy and cheat because they are unhappy, not necessarily because they make less money."
Ironically, men who make significantly more than their female partners were also more likely to cheat. "At one end of the spectrum, making less money than a female partner may threaten men's gender identity by calling into question the traditional notion of men as breadwinners," Munsch said. "At the other end of the spectrum, men who make a lot more money than their partners may be in jobs that offer more opportunities for cheating like long work hours, travel, and higher incomes that make cheating easier to conceal."
Putting all of these numbers in context, Munsch said that very few people cheat on their partners (or report doing so in a survey). An average of approximately 3.8% of male partners and 1.4% of female partners cheated in any given year during the six-year period studied.
The study also found that women who were financially dependent on their male partners were less likely to cheat than women who made the same as or more than their male partners. For example, women who were completely dependent on their male partner's income were 50% less likely to cheat than women who made the same amount of money as their partner, and 75% less likely than women who contributed most or all of the household income. This relationship holds true even when taking into account age, education level, income, religious attendance, and relationship satisfaction.
"For women, making less money than a male partner is not threatening, it is the status quo," said Munsch. "More importantly, economically dependent women may encounter fewer opportunities to cheat, and they may make a calculated decision that cheating just isn't worth it. If they get caught, their livelihood is at risk."