See below for a link to an article discussing the study and for a link for the actual study itself. tl;dr women underreport their sexual activity and men overreport due to societal pressure.

https://news.osu.edu/men-women-lie-about-sex-to-match-gender-expectations/

https://www.researchgate.net/publication/257663739_Gender_Roles_and_Pressure_to_be_Truthful_The_Bogus_Pipeline_Modifies_Gender_Differences_in_Sexual_but_Not_Non-sexual_Behavior

While this study is limited and somewhat dated, the results can still be applied to sex studies being done today. The results should hardly be controversial as it simply suggests people are somewhat self conscious about sex and feel some shame when not meeting societal expectations.

When reviewing the results of self reported sex surveys, keep this study in mind. But if men and faced less societal pressures related to sex, then self reported sex studies would be more accurate.