According to The New York Times, the most consistent data on infidelity comes from the University of Chicago's General Social Survey (GSS).
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.
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.
These findings suggest there may be various factors that might influence the likelihood of some individuals to engage in extradyadic relationships, and that such factors may account for observed gender differences beyond actual gender and evolutionary pressures associated with each.
In one study by Blow, rates were higher in more recent marriages, compared with previous generations.
A study by Liu found that the likelihood for women to be involved in infidelity reached a peak in the seventh year of their marriage and then declined afterwards; whereas for married men, the longer they are in relationships the less likely they are to engage in infidelity, except for the eighteenth year of marriage, at which point the chance that men will engage in infidelity increases.