By the 1950s in the United Kingdom, it was thought that about fifteen percent of male homosexuals had anal sex.[Full citation needed] More recent studies, The Gay Urban Men's Study (P.I. Stall, UCSF) and the Young Men's Study (YMS, PI Osmond/Catania, UCSF), indicate that 50% of the surveyed men who have sex with men engage in anal sex.[Full citation needed] [Full citation needed] The 1994 Laumann study suggests that 80% of gay men practice it and 20% never engage in it at all.
You mite also want to use the studies of actual homosexuals.
Just wanted to add this from your source...
The National Institutes of Health (NIH), with information published in the British Medical Journal (BMJ), states that two thirds of gay men have anal sex. Other sources suggest that roughly three-fourths of gay men have anal sex at one time or another in their lives, with an equal percentage participating as tops and bottoms. A survey in The Advocate in 1994 indicated that 46% of gay men preferred to penetrate their partners, while 43% preferred to be the receptive partner. A survey conducted from 1994 to 1997 in San Francisco by the Stop AIDS Project indicated that over the course of the study, among men who have sex with men, the proportion engaging in anal sex increased from 57.6% to 61.2%.