Approximately how many percent couples perform anal sex?

Is it normat.My girlfriends not agreed for this.Approximately how many percent couples perform anal sex?
The US Center for Disease Control determined in a 2005 survey that the prevalence of anal intercourse in the US heterosexual population is on the rise. The survey showed that 40 percent of men and 35 percent of women between 25 and 44 had engaged in heterosexual anal sex; in 1992 a similar survey found that only 25.6 percent of men 18 to 59 and 20.4 percent of women 18 to 59 had engaged. By way of comparison, seven times as many women as gay men engage in anal intercourse, a figure reflecting the greater overall heterosexual population. Another survey in 2008 indicates that anal sex is on the rise amongst young people; the survey, which focused on a much younger demographic of teens and young adults aged 15鈥?1, found that 16 percent of 1350 surveyed had had anal sex in the previous 3 months with condoms being used 29% of the time.Approximately how many percent couples perform anal sex?
difficult to say but to best of my knowledge 20 % couples try anal sex once in a while.