College students mostly use birth control while a small high-activity minority never does.

Evidence

In January 1992, I pursued the issue again, asking, “If you are not a virgin, for the past year, what percent of the time when you engaged in sexual intercourse, did you use some reasonably trustworthy way of preventing pregnancy? (That is, the ‘pill,’ an IUD or diaphragm with spermicidal foam, or a condom?)” This time males reported an average of 79.2%, and females 86.6% (p > .20). Thus students usually took precautions against pregnancy: 66% of the females and 60% of the males reported using such birth control devices 100% of the time. The seven females and twelve males I found who never, or almost never, practiced birth control usually had low levels of sexual activity (for example, “two partners, one time with each”). But one female reported she had had sex 130 times with her boyfriend and they had never used any protection. Another woman said she had had sex 50 times with ten different men, and practiced birth control only 10% of the time. Then there was the guy who had had intercourse 200 times with forty different partners, and another who figured he was “close to 1,000” with ‘about thirty-five” women, who had never taken any precautions against impregnation. — Bob Altemeyer, The Authoritarian Specter, 2331