The U.S. Census Bureau has never surveyed individuals regarding their sexual orientation. For the first time, however, in the 2020 census, the agency gave individuals the opportunity to identify their relationship (and specifically their marital relationship) as same-sex. This only provided the count of those living within the same household in marital or partner relationships.
The most informative survey offering any view of Los Angeles County’s LGBTQ population was a Gallup survey of more than 374,000 people, conducted from June 2012 through December 2012, that asked the question, "Do you, personally, identify as lesbian, gay, bisexual or transgender?" The survey focused on the 50 largest metropolitan areas in the United States, including the Los Angeles area. It found the Los Angeles-Long Beach-Anaheim metropolitan area (Los Angeles and Orange Counties) to rank eighth among America’s 50 largest metro areas, with 4.6 percent of its population identifying as LGBTQ. Although Gallup, at the time, put the national average that dentified as LGBTQ at 3.6 percent, its 2020 survey updated that to 5.6 percent (likely also increasing the L.A. metro area percentage).
If we were to apply the 4.6 percent survey finding against the most recent U.S. Census estimate (2019) for Los Angeles County’s adult population, we could estimate that 361,658 adult residents of the county are LGBTQ. About the same time, a 2012 report by the Los Angeles County Department of Public Health estimated that 14,428 county residents are transgender.
In 2018, U.S. Census estimates for number of households in which unmarried partners were the same sex came to 15,606 (5,813 same-sex female partners and 9,793 same-sex male partners). This was about half the census count of unmarried same-sex partner households in the 2010 Census (32,704). Perhaps, this may have been due to many of these couples marrying by 2018, inasmuch as California recognized same-sex marriage in 2013. Of the 2010 same-sex unmarried partner households, 25 percent had related children under the age of 18.