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."Demographics of the Gay and Lesbian Population in the United States: Evidence from Available Systematic Data Sources", Dan Black, Gary Gates, Seth Sanders, Lowell Taylor, Demography, Vol. 37, No. 2 (May, 2000), pp. 139–154 (available on JSTOR). 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.LeVay, Simon (1996). Queer Science: The Use and Abuse of Research into Homosexuality. Cambridge: The MIT Press 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.Sexual Behavior in the Human Male, p. 656 Kinsey's methodology was criticized. John Tukey criticizes sample procedure A later study tried to eliminate the sample bias, but still reached similar conclusions. Martin Duberman on Gebhart's "cleaning" of data

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.Bogaert, A. F. (2004). The prevalence of male homosexuality: The effect of fraternal birth order and variation in family size. Journal of Theoretical Biology, 230, 33–37. Laumann, E. O., Gagnon, J. H., Michael, R. T., & Michaels, S. (1994). The social organization of sexuality: Sexual practices in the United States. Chicago: University of Chicago Press.Wellings, K., Field, J., Johnson, A., & Wadsworth, J. (1994). Sexual behavior in Britain: The national survey of sexual attitudes and lifestyles. London, UK: Penguin Books.McConaghy et al., 2006S. Hite, The Hite Report on Male Sexuality, New York, A. Knopf, 1991.S. S. et C. L. Janus, The Janus Report on Sexual Behavior, New York, John Wiley & Sons, 1993.Alfred C. Kinsey, Sexual Behavior in the Human Male, 1948, (o.p.), (reprint).

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.

Employment discrimination refers to discriminatory employment practices such as bias in hiring, promotion, job assignment, termination, and compensation, and various types of harassment. In the United States there is "very little statutory, common law, and case law establishing employment discrimination based upon sexual orientation as a legal wrong." § 5:17 Some exceptions and alternative legal strategies are available. President Bill Clinton's Executive Order 13087 (1998) prohibits discrimination based on sexual orientation in the competitive service of the federal civilian workforce, and federal non-civil service employees may have recourse under the Due Process Clause of the U.S. Constitution.Ashton v. Civiletti, 613 F.2d 923, 20 Fair Empl. Prac. Cas. (BNA) 1601, 21 Empl. Prac. Dec. (CCH) P 30297 (D.C. Cir. 1979) Private sector workers may have a Title VII action under a quid pro quo sexual harassment theory,Kelly v. City of Oakland, 198 F.3d 779, 81 Fair Empl. Prac. Cas. (BNA) 1455, 77 Empl. Prac. Dec. (CCH) P 46281 (9th Cir. 1999) a "hostile work environment" theory,Oncale v. Sundowner Offshore Services, Inc., 523 U.S. 75, 118 S. Ct. 998, 1002 (1998) a sexual stereotyping theory,Price Waterhouse v. Hopkins, or others. Housing discrimination refers to discrimination against potential or current tenants by landlords. In the United States, there is no federal law against such discrimination on the basis of sexual orientation or gender identity, but at least thirteen states and many major cities have enacted laws prohibiting it. Hate crimes (also known as bias crimes) are crimes motivated by bias against an identifiable social group, usually groups defined by race, religion, sexual orientation, disability, ethnicity, nationality, age, gender, gender identity, or political affiliation. In the United States, 45 states and the District of Columbia have statutes criminalizing various types of bias-motivated violence or intimidation (the exceptions are AZ, GA, IN, SC, and WY). Each of these statutes covers bias on the basis of race, religion, and ethnicity; 32 of them cover sexual orientation, 28 cover gender, and 11 cover transgender/gender-identity. In October 2009, the Matthew Shepard and James Byrd, Jr. Hate Crimes Prevention Act, which "...gives the Justice Department the power to investigate and prosecute bias-motivated violence where the perpetrator has selected the victim because of the person's actual or perceived race, color, religion, national origin, gender, sexual orientation, gender identity or disability," was signed into law and makes hate crime based on sexual orientation, amongst other offenses, a federal crime in the United States.

Political activism

Since the 1960s, many LGBT people in the West, particularly those in major metropolitan areas, have developed a so-called gay culture. To many, gay culture is exemplified by the gay pride movement, with annual parades and displays of rainbow flags. Yet not all LGBT people choose to participate in "queer culture", and many gay men and women specifically decline to do so. To some it seems to be a frivolous display, perpetuating gay stereotypes. To some others, the gay culture represents heterophobia and is scorned as widening the gulf between gay and non-gay people.

With the outbreak of AIDS in the early 1980s, many LGBT groups and individuals organized campaigns to promote efforts in AIDS education, prevention, research, patient support, and community outreach, as well as to demand government support for these programs. Gay Men's Health Crisis, Project Inform, and ACT UP are some notable American examples of the LGBT community's response to the AIDS crisis.

The bewildering death toll wrought by the AIDS epidemic at first seemed to slow the progress of the gay rights movement, but in time it galvanized some parts of the LGBT community into community service and political action, and challenged the heterosexual community to respond compassionately. Major American motion pictures from this period that dramatized the response of individuals and communities to the AIDS crisis include An Early Frost (1985), Longtime Companion (1990), And the Band Played On (1993), Philadelphia (1993), and Common Threads: Stories from the Quilt (1989), the last referring to the NAMES Project AIDS Memorial Quilt, last displayed in its entirety on the Mall in Washington, D.C., in 1996.

Publicly gay politicians have attained numerous government posts, even in countries that had sodomy laws in their recent past. Examples include Guido Westerwelle, Germany's Vice-Chancellor; Peter Mandelson, a British Labour Party cabinet minister and Per-Kristian Foss, formerly Norwegian Minister of Finance.

LGBT movements are opposed by a variety of individuals and organizations. Some social conservatives believe that all sexual relationships with people other than an opposite-sex spouse undermine the traditional family and that children should be reared in homes with both a father and a mother. There is concern that gay rights may conflict with individuals' freedom of speech, religious freedoms in the workplace, the ability to run churches, charitable organizations and other religious organizations in accordance with one's religious views, and that the acceptance of homosexual relationships by religious organizations might be forced through threatening to remove the tax-exempt status of churches whose views don't align with those of the government.

Critics charge that political correctness has led to the association of sex between males and HIV being downplayed.

Relationships