section_path: Behaviors/Prevalence
section_name: Prevalence
paragraph_text: Prevalence
  
  Penile–vaginal penetration is the most common form of sexual intercourse. Studies indicate that most heterosexual couples engage in vaginal intercourse nearly every sexual encounter. The National Survey of Sexual Health and Behavior (NSSHB) reported in 2010 that vaginal intercourse is "the most prevalent sexual behavior among men and women of all ages and ethnicities". Clint E. Bruess et al. stated that it "is the most frequently studied behavior" and is "often the focus of sexuality education programming for youth." Weiten et al. said that it "is the most widely endorsed and practiced sexual act in our society."
  
  Regarding oral or anal intercourse, the CDC stated in 2009, "Studies indicate that oral sex is commonly practiced by sexually active male-female and same-gender couples of various ages, including adolescents." Oral sex is significantly more common than anal sex. The 2010 NSSHB study reported that vaginal intercourse was practiced more than insertive anal intercourse among men, but that 13% to 15% of men aged 25 to 49 practiced insertive anal intercourse. Receptive anal intercourse was infrequent among men, with approximately 7% of men aged 14 to 94 years old having said that they were a receptive partner during anal intercourse. The study said that fewer women reported engaging in anal sex than other partnered sexual behaviors. It was estimated that 10% to 14% of women aged 18 to 39 years old practiced anal sex in the past 90 days, and that most of the women who engage in anal sex said they practiced it once a month or a few times a year.