http://www.huffingtonpost.com/2012/01/06/anal-sex-heterosexual-couples-report_n_1190440.html

Though its practice is frequently assumed to be confined to the gay male population, anal intercourse appears to be more popular than possibly expected among heterosexual couples under 45, according to a Center for Disease Control and Prevention (CDC) report.

The report, titled "Sexual Behavior, Sexual Attraction and Sexual Identity in the United States," which reportedly polled thousands of people between the ages of 15 and 44 from 2006 through 2008, found that 44 percent of straight men and 36 percent of straight women admitted to having had anal sex at least once in their lives.

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There have been several published theories as to the reason for a rise in popularity (and we can hopefully assume it's not an increase in the number of people Googling Rick Santorum). A Dec. 22, 2011 piece by Hugo Schwyzer, a professor of gender studies and history at Pasadena City College, implied that anal sex (which he calls "the most selfless of common sexual acts" given the amount of pain the "bottoming" partner endures in its practice) could be on the rise due to its frequent appearance in both heterosexual porn and mainstream media as well as an increased pressure from heterosexual male partners. He also cited several sources who seemed to cast doubt on how pleasurable the act was for women.