Results, however, vary year by year, and also by age-group surveyed.
Depending on the context, men and women can experience social consequences if their act of infidelity becomes public.The form and extent of these consequences are often dependent on the gender of the unfaithful person.One measure of infidelity among couples is the frequency of children secretly conceived with a different partner, leading to "non-paternities".Such covertly illegitimate children amount to about 1–2% of newborns in European populations.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.
According to The New York Times, the most consistent data on infidelity comes from the University of Chicago's General Social Survey (GSS).
Interviews with people in non-monogamous relationships since 1972 by the GSS have shown that approximately 12% of men and 7% of women admit to having had an extramarital relationship.
Studies suggest around 30–40% of unmarried relationships and 18–20% of marriages see at least one incident of sexual infidelity.
Rates of infidelity among women are thought to increase with age.
In terms of infidelity, the theory states that when sex-ratios are high, men are more likely to be promiscuous and engage in sex outside of a committed relationship because the demand for men is higher and so this type of behaviour, which is desired by men, is more accepted.