Such covertly illegitimate children amount to about 1–2% of newborns in European populations.
According to The New York Times, the most consistent data on infidelity comes from the University of Chicago's General Social Survey (GSS).
Treas and Giesen found that people who had stronger sexual interests, more permissive sexual values, lower subjective satisfaction with their partner, weaker network ties to their partner, and greater sexual opportunities were more likely to be unfaithful.
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".
Article uses three different citation styles: inline footnotes, a "references section" and a "further reading" section. For example, the first citation, Leeker & Carlozzi, points to the further reading section. Other scholars define infidelity as a violation according to the subjective feeling that one's partner has violated a set of rules or relationship norms; this violation results in feelings of sexual jealousy and rivalry.
The second citation (Weeks) is both defined in text and pointed at using a footnote. In marital relationships, exclusivity expectations are commonly assumed although they are not always met.
On the other hand, when sex ratios are low, promiscuity is less common because women are in demand and since they desire monogamy and commitment, in order for men to remain competitive in the pool of mates, they must respond to these desires.