OK, starting from the total USA population of about three hundred million, let's subtract.
By the time women in the USA reach college age, nearly 20 percent have been approached sexually by a family member. (some areas report higher incidence, some lower - Los Angeles, for example, had a stated rate of over 27 percent of women who had actually been involved in incest.
That's attempted incest in all forms; consensual and non-consensual (rape). That's about 60 million women in the USA. Rape incest ranges in estimates from 14 million to 19 million women.
Of that 60 million number, only about 4 or 5 percent will accept, or have consensual incest. Say about 3 million women. Most actual incest is also child sexual abuse or rape, so if we leave out the non-consensual incest, we arrive at a total of approximately 6 million including males.
Consensual Incest remains, naturally, highly under-reported (over 30 percent never tell anyone), so all the statistics mentioned here are compiled estimates, taken from several sources.
· 1 decade ago