Support for this theory comes from evidence showing higher divorce rates in countries with lower sex ratios and higher monogamy rates in countries with higher sex ratios.Differences in sexual infidelity as a function of gender have been commonly reported.
One measure of infidelity is covert illegitimacy, a situation which arises when someone who is presumed to be a child's father (or mother) is in fact not the biological father (or mother).
Frequencies as high as 30% are sometimes assumed in the media, but research Such studies show that covert illegitimacy is in fact less than 10% among the sampled African populations, less than 5% among the sampled Native American and Polynesian populations, less than 2% of the sampled Middle Eastern population, and generally 1–2% among European samples.
Results, however, vary year by year, and also by age-group surveyed.
For example, one study conducted by the University of Washington, Seattle found slightly, or significantly higher rates of infidelity for populations under 35, or older than 60.
For example, one study found that some women in more financially independent and higher positions of power, were also more likely to be more unfaithful to their partners.