Estimates of the percentage of people who cheat vary widely depending on the demographic being surveyed and how data is collected. Here are some key findings from the search results:

• According to estimates based on married couples, approximately 25% of men admit to cheating on their spouse at some point, while around 15% of women admit to the same.
• Another estimate from the journal of Marriage and Divorce concludes that 70% of married Americans cheat at least once in their marriage.
• According to the General Social Survey, 20% of married men and 13% of married women admitted to having sex with someone other than their spouse.
• At the higher end of estimates, 75% of men and 68% of women admitted to cheating in some way, at some point, in a relationship.
• However, its important to note that not everyone defines cheating in the same way, and some people may have difficulty admitting to cheating.

Overall, its difficult to determine an exact percentage of people who cheat, but its clear that infidelity is not uncommon in relationships.