In this era of frequent political scandal over infidelity, it is worth looking at the data on what Americans say about the issue. 

The General Social Survey (GSS), a nationally representative sample of American adults conducted by the National Opinion Research Center (NORC) at the University of Chicago, has asked the same two questions about extramarital sex numerous times since 1988 -- "Have you ever had sex with someone other than your spouse while married?" and "Have you had sex with someone other than your spouse while married during the last 12 months?"

• 3-4% say yes, last 12 months; and
• 15-18% say yes, ever.

Read the entire analysis, American Sexual Behavior, by Tom W. Smith.

The General Social Survey is sponsored by the National Science Foundation and other groups.  Click here to learn more about the GSS.