Homosexuality, as a phenomenon and as a behavior, has existed throughout all eras in human societies.
Demographics
Reliable data as to the size of the gay and lesbian population is of value in informing public policy. For example, demographics would help in calculating the costs and benefits of domestic partnership benefits, of the impact of legalizing gay adoption, and of the impact of the U.S. military's Don't ask, don't tell policy. Further, knowledge of the size of the "gay and lesbian population holds promise for helping social scientists understand a wide array of important questions—questions about the general nature of labor market choices, accumulation of human capital, specialization within households, discrimination, and decisions about geographic location."
Measuring the prevalence of homosexuality may present difficulties. The research must measure some characteristic that may or may not be defining of sexual orientation. The class of people with same-sex desires may be larger than the class of people who act on those desires, which in turn may be larger than the class of people who self-identify as gay/lesbian/bisexual.
In 1948 and 1953, Alfred Kinsey reported that nearly 46% of the male subjects had "reacted" sexually to persons of both sexes in the course of their adult lives, and 37% had had at least one homosexual experience. Kinsey's methodology was criticized. A later study tried to eliminate the sample bias, but still reached similar conclusions.
Estimates of the occurrence of exclusive homosexuality range from one to twenty percent of the population, usually finding there are slightly more gay men than lesbians.
Estimates of the frequency of homosexual activity also vary from one country to another. A 1992 study reported that 6.1% of males in Britain had had a homosexual experience, while in France the number was 4.1%. According to a 2003 survey, 12% of Norwegians have had homosexual sex. In New Zealand, a 2006 study suggested that 20% of the population anonymously reported some homosexual feelings, few of them identifying as homosexual. Percentage of persons identifying homosexual was 2–3%. According to a 2008 poll, while only 6% of Britons define their sexual orientation as homosexual or bisexual, more than twice that number (13%) of Britons have had some form of sexual contact with someone of the same sex.
In the United States, according to exit polling on 2008 Election Day for the 2008 Presidential elections, 4% of electorate self-identified as gay, lesbian, or bisexual, the same percentage as in 2004." An estimated 34,000 homosexuals who are in a relationship are employed by the federal government.
Law
Most nations do not impede consensual sex between unrelated persons above the local age of consent. Some jurisdictions further recognize identical rights, protections, and privileges for the family structures of same-sex couples, including marriage. Some nations mandate that all individuals restrict themselves to heterosexual relationships; that is, in some jurisdictions homosexual activity is illegal. Offenders can face the death penalty in some fundamentalist Muslim areas such as Iran and parts of Nigeria. There are, however, often significant differences between official policy and real-world enforcement. See Violence against LGBT people.
Although homosexual acts were decriminalized in some parts of the Western world, such as Poland in 1932, Denmark in 1933, Sweden in 1944, and the United Kingdom in 1967, it was not until the mid-1970s that the gay community first began to achieve limited civil rights in some developed countries. On July 2, 2009, homosexuality was decriminalized in India by a High Court ruling. A turning point was reached in 1973 when the American Psychiatric Association removed homosexuality from the Diagnostic and Statistical Manual of Mental Disorders, thus negating its previous definition of homosexuality as a clinical mental disorder. In 1977, Quebec became the first state-level jurisdiction in the world to prohibit discrimination on the grounds of sexual orientation. During the 1980s and 1990s, most developed countries enacted laws decriminalizing homosexual behavior and prohibiting discrimination against lesbian and gay people in employment, housing, and services. On the other hand, many countries today in the Middle East and Africa, as well as several countries in Asia, the Caribbean and the South Pacific, outlaw homosexuality. In six countries, homosexual behavior is punishable by life imprisonment; in ten others, it carries the death penalty.