This is so obvious. Aside from the promotion of promiscuity in the schools and the culture, a primary driver of the STD epidemic is hormonal contraceptives. When the girls are taking pills, patches, or shots, the motivation for condom use goes way down.
Wake up, girls! Guys don't care if you get pregnant, and they don't care if you get a potentially fatal disease. Tell them to leave you alone!
For a long time I wondered why there was no male contraceptive analogous to The Pill, and then I realized it was for this very reason. Women won't trust men to use it. That kind of mistrust is a horrible basis for a deep relationship.