Measuring the prevalence of various sexual orientations is difficult because there is a lack of reliable data. Sexual orientation is believed to refer to "an enduring pattern of emotional romantic and/or sexual attractions to men women or both sexes Sexology is the study of sexual interests behavior and function Asexuality is a Sexual orientation that describes individuals who do not experience Sexual attraction. Autosexuality refers to Sexual orientation and sexual behavior of attraction or romance that one holds exclusively and expresses towards oneself Bisexuality refers to sexual behavior with or attraction to people of both sexes or to a bisexual orientation Heterosexuality refers to sexual behavior with or attraction to people of the opposite sex or to a heterosexual orientation Homosexuality refers to sexual behavior with or attraction to people of the same sex or to a Homosexual orientation. Pansexuality or anthrosexuality ( anthro- literally meaning human human sexual (sometimes referred to as omnisexuality) is a Sexual orientation Pomosexual, or undefined sexual orientation, is a Neologism used to describe a person who shuns Sexual orientation labels (such as heterosexual and homosexual Zoophilia Zoosexuality is a term used to describe a Sexual orientation towards non-human animals In the English language, gay is an Adjective that in modern usage refers to Homosexuality. A lesbian is a Woman who is romantically or sexually attracted only to other women Queer has traditionally meant odd or unusual but is now also used to refer to anyone who is not heteronormative. Questioning is a term that can refer to a person who is questioning their Gender, Sexual identity or Sexual orientation. The Kinsey scale attempts to describe a person's sexual history or episodes of their sexual activity at a given time The Klein Sexual Orientation Grid attempts to further measure Sexual orientation by expanding upon the earlier Kinsey scale which categorizes sexual history from 0 Biology and sexual orientation is research into possible biological influences on the development of human Sexual orientation. Intersexuality is the state of a living thing of a gonochoristic species whose Sex chromosomes, Genitalia, and/or Secondary sex characteristics Transgender (trænzˈdʒɛndɚ from ( Latin) derivatives Transsexualism is a condition in which a person identifies with a physical Sex different from the one with which they were born Sexual orientation is believed to refer to "an enduring pattern of emotional romantic and/or sexual attractions to men women or both sexes Problems gathering data include:
Another significant distinction can be made between what medical statisticians call incidence and prevalence. Incidence is a measure of the risk of developing some new condition within a specified period of time In Epidemiology, the prevalence of a Disease in a Statistical population is defined as the total number of cases of the disease in the population at a given For example, even if two studies agree on a common criterion for defining a sexual orientation, one study might regard this as applying to any person who has ever met this criterion, whereas another might only regard them as being so if they had done so during the year of the survey.
Reliable data as to the size of the gay and lesbian population would be valuable by 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 US military's Don't Ask Don't Tell policy. A domestic partnership is a legal or Personal relationship between two individuals who live together and share a common domestic life but are neither joined by a traditional LGBT adoption refers to the Adoption of children by Lesbian, Gay, Bisexual, or Transgendered people "Don't ask don't tell" is the common term for the policy about homosexuality in the U  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. "
Two of the most famous studies of the demographics of human sexual orientation were Dr. Alfred Kinsey's Sexual Behavior in the Human Male (1948) and Sexual Behavior in the Human Female (1953). Alfred Charles Kinsey (June 23 1894 &ndash August 25 1956 was an American Biologist and professor of Entomology and Zoology, who in 1947 These studies used a seven-point spectrum to define sexual behavior, from 0 for completely heterosexual, to 6 for completely homosexual. Kinsey concluded that all but a small percentage of the population were to one degree or another bisexual (falling on the scale from 1 to 5). He also reported that 37% of men in the U. S. had achieved orgasm through contact with another male after adolescence and 13% of women had achieved orgasm through contact with another woman. An orgasm (sexual climax is the conclusion of the plateau phase of the sexual response cycle, and may be experienced by both males and females 
His results, however, have been disputed, especially in 1954 by a team consisting of John Tukey, Frederick Mosteller and William G. Cochran, who stated much of Kinsey's work was based on convenience samples rather than random samples, and thus would have been vulnerable to bias. John Wilder Tukey ( June 16, 1915 &ndash July 26, 2000) was an American Statistician. Charles Frederick Mosteller ( December 24, 1916 - July 23, 2006, usually known as Frederick Mosteller or Fred was one of the most William Gemmell Cochran ( 15 July 1909 – 29 March 1980) was a prominent statistician; he was born in Scotland but spent Sampling is that part of Statistical practice concerned with the selection of individual observations intended to yield some knowledge about a population of concern A sample is a subject chosen from a population for investigation Bias is a term used to describe a Tendency or Preference towards a particular perspective, Ideology or result especially when the tendency interferes 
Paul Gebhard, Kinsey's successor as director of the Kinsey Institute for Sex Research, dedicated years to reviewing the Kinsey data and culling its purported contaminants. Paul H Gebhard (born July 3, 1917) was an American Anthropologist and Sexologist. The Kinsey Institute for Research in Sex Gender and Reproduction, often shortened to The Kinsey Institute, exists "to promote interdisciplinary research and scholarship In 1979, Gebhard (with Alan B. Johnson) concluded that none of Kinsey's original estimates were significantly affected by the perceived bias, finding that 36. 4% of men had engaged in both heterosexual and homosexual activities, as opposed to Kinsey's 37%.
In general, surveys quoted by anti-gay activists tend to show figures nearer 1%, while surveys quoted by gay activists tend to show figures nearer 10%, with a mean of 4-5% figure most often cited in mainstream media reports.
It is important to note, however, that these numbers are subject to many of the pitfalls inherent in researching sensitive social issues. It is possible that survey results may be biased by under-reporting, for instance. (See note 1. Measurement difficulties Measuring the prevalence of various Sexual orientations is difficult because there is a lack of Reliable data. ) The frequent use of non-random samples (white college students) in many studies could also serve to skew the data. A sample is a subject chosen from a population for investigation
In general, most research agrees that the number of people who have had multiple same-gender sexual experiences is fewer than the number of people who have had a single such experience, and that the number of people who identify themselves as exclusively homosexual is fewer than the number of people who have had multiple homosexual experiences.
In addition, major historical shifts can occur in reports of the prevalence of homosexuality. For example, the Hamburg Institute for Sexual Research conducted a survey over the sexual behavior of young people in 1970, and repeated it in 1990. Hamburg (English, German: ˈhambʊɐk local pronunciation Low German / Low Saxon: Hamborg) is the second-largest city in Germany Whereas in 1970 18% of the boys aged 16 and 17 reported to have had same-sex sexual experiences, the number had dropped to 2% by 1990.  "Ever since homosexuality became publicly argued to be an innate sexual orientation, boys' fear of being seen as gay has, if anything, increased," the director of the institute, Volkmar Sigusch, suggested in a 1998 article for a German medical journal. 
In 2005, as part of the statistical and financial measurements required to implement the UK's new Civil Partnership Act, the British government's H. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located See Civil partnerships in the United Kingdom for a detailed discussion of the Act and its implementation. M. Treasury actuaries calculated that there are 3. 6 million British people who may want to enter into a gay or lesbian civil partnership arrangement. This is equal to around 6 percent of the UK population.
These charts show a list of the top 10 US metropolitan areas with the highest GLB population in terms of numbers of total gay, lesbian and bisexual residents. A gay village (also known as a gay neighborhood or by the slang gayborhood) is an urban geographic location with generally recognized boundaries 
|1||San Francisco||15. The City and County of San Francisco is the fourth most populous city 4%||94,234||4|
|7||Portland||8. Portland is a city located in the Northwestern United States, near the Confluence of the Willamette and Columbia rivers 8%||35,413||14|
|8||Denver||8. The City and County of Denver (pronounced /ˈdɛnvɚ/ is the Capital and the most populous city of Colorado, in the United States 2%||33,698||17|
|9||Washington||8. Washington DC ( formally the District of Columbia and commonly referred to as Washington, the District, or simply D 1%||32,599||18|
|10||Orlando||7. Orlando is a major City in central Florida, USA and is the County seat of Orange County Florida. 7%||12,508||36|
|1||New York City - Northern New Jersey - Long Island, NY||568,903||2. The City of New York North Jersey is a name for the northern part of the US State of New Jersey, which is sandwiched between two important cities New York City (which North Long Island is an island located in southeastern New York, USA, its western shores directly across from Manhattan, from which the island stretches 6%|
|2||Los Angeles - Long Beach, CA - Santa Ana, CA||442,211||2. Los Angeles (lɑˈsændʒələs los ˈaŋxeles in Spanish) is the largest City in the state of California and the American West Long Beach is a city located in southern California, USA, on the Pacific coast Founded in 1869 Santa Ana ( is the most populous city in Orange County California and is the County seat and a city of about 353184 people. 7%|
|3||Chicago–Naperville–Joliet, IL||288,478||3. The Chicago metropolitan area is the Metropolitan area associated with the city of Chicago in the United States and its suburbs 1%|
|4||San Francisco - Oakland - Fremont, CA||256,313||3. The City and County of San Francisco is the fourth most populous city Oakland (ˈoʊklənd founded in 1852 is the eighth-largest city in the U Fremont (ˈfriːmɒnt is a city in California, USA that was incorporated on January 23, 1956, from the merger of five smaller communities Centerville 6%|
|5||Boston - Cambridge, MA - Quincy, MA||201,344||3. Cambridge Massachusetts is a City in the Greater Boston area of Massachusetts, United States. Quincy is a city in Norfolk County, Massachusetts, United States. 4%|
|6||Washington DC||191,959||2. Washington DC ( formally the District of Columbia and commonly referred to as Washington, the District, or simply D 5%|
|7||Dallas - Fort Worth - Arlington, TX||183,718||3. Fort Worth is the fifth-largest city in the state of Texas and the seventeenth-largest city in the United States. Arlington is a Suburb of Fort Worth in Tarrant County, Texas ( USA) within the Dallas-Fort Worth-Arlington metropolitan area 5%|
|8||Miami - Miami Beach - Fort Lauderdale||183,346||4. Fort Lauderdale, known as the "Venice of America" due to its expansive and intricate Canal system is a city in Broward County, Florida, 7%|
|9||Atlanta - Marietta, GA - Sandy Springs, GA||180,168||4. Marietta is a City located in central Cobb County Georgia, and is its County seat. Sandy Springs is a newly incorporated city incorporated in December 2005 3%|
|10||Philadelphia - Camden, NJ - Wilmington, DE||179,459||2. Philadelphia (ˌfɪləˈdɛlfiə The City of Camden is the County seat of Camden County, New Jersey, in the United States. Wilmington is the largest city in the state of Delaware, United States and is located at the confluence of the Christina River and Brandywine 8%|