-Цитата от Владимир

но что то мне подсказывает, что их процент в обществе, на протяжении всех времен остается более или менее постоянным

а мне что-то подсказывает обратное.
в статистиках гуглов путаница, т.к одни опросы о том, if you ever had homosexual experience, а другие - do you identify yourself as a gay person, или ever experienced same-sex attraction т.е абсолютно разные вещи

Омерика, например:


1990–92
The American National Health Interview Survey conducts household interviews of the civilian non-institutionalized population. The results of three of these surveys, done in 1990–91 and based on over 9,000 responses each time, found between 2–3% of the people responding said yes to a set of statements which included "You are a man who has had sex with another man at some time since 1977, even one time."[7]
1992
The National Health and Social Life Survey asked 3,432 respondents whether they had any homosexual experience. The findings were 1.3% for women within the past year, and 4.1% since 18 years; for men, 2.7% within the past year, and 4.9% since 18 years.[8]
1993
The Alan Guttmacher Institute of sexually active men aged 20–39 found that 2.3% had experienced same-sex sexual activity in the last ten years, and 1.1% reported exclusive homosexual contact during that time.[9]

1990
An extensive study on sexuality in general was conducted in the United States. A significant portion of the study was geared towards homosexuality. The results found that 8.6% of women and 10.1% of men had at one point in their life experienced some form of homosexuality. Of these, 87% of women and 76% of men reported current same-sex attractions, 41% of women and 52% of men had sex with someone of the same gender, and 16% of women and 27% of men identified as LGBT.[6]

2011 - 19 million Americans, or 8.2 percent of the population, said they have engaged in same-sex behavior, сообщает Williams Institute

т.е 2-3-4% в 1990 и ~8% в 2011

но какого-либо детального анализа не нашёл