linguistic:paraphrasing, structural:scholar_edition
Prevalence

According to the paper "Estimating the prevalence and career longevity of prostitute women", the number of full-time equivalent prostitutes in a typical area in the United States (Colorado Springs, CO, during 1970–1988) is estimated at 23 per 100,000 population (0.023%), of which some 4% were under 18. The length of these prostitutes' working careers was estimated at a mean of 5 years. According to a 2012 report by Fondation Scelles there are between 40 and 42 million prostitutes in the world.

In 2003, it was estimated that in Amsterdam, one woman in 35 was working as a prostitute, compared to one in 300 in London.

The number of men who have used a prostitute at least once varies widely from country to country, from an estimated low of between 7% and 8.8% in the United Kingdom, to a high of between 59% and 80% in Cambodia. A study conducted by ProCon – a nonpartisan nonprofit organization – estimated the percentage of men who had paid for sex at least once in their lives, and found the highest rates in Cambodia (between 59 and 80% of men had paid for sex at least once) and Thailand (an estimated 75%), followed by Italy (16.7–45%), Spain (27–39%), Japan (37%), the Netherlands (13.5–21.6%), the United States (15.0–20.0%), and China (6.4-20%). Nations with higher rates of prostitution clients display much more positive attitudes towards commercial sex. In some countries, such as Cambodia and Thailand, sex with prostitutes is considered commonplace and men who do not engage in commercial sex may be considered unusual by their peers. In Thailand, it has been reported that about 75% of men have visited a prostitute at least once in their lifetimes. In Cambodia, that figure is 59% to 80%.

In the United States, a 2004 TNS poll reported 15% of all men admitted to having paid for sex at least once in their life. However, a paper entitled "Prostitution and the sex discrepancy in reported number of sexual partners" concluded that men's self-reporting of prostitutes as sexual partners provides a serious underestimate.

In Australia, a survey conducted in the early 2000s showed that 15.6% of men aged 16–59 reported paying for sex at least once in their life, and 1.9% had done so in the past year.

Reports disagree on whether prostitution levels are growing or declining in developed countries. Some studies indicate that the percentage of men engaging in commercial sex in the United States has declined significantly in recent decades: in 1964, an estimated 69–80% of men had paid for sex at least once. Some have suggested that prostitution levels have fallen in sexually liberal countries, most likely because of the increased availability of non-commercial, non-marital sex or, for example in Sweden, because of stricter legal penalties. Other reports suggest a growth in prostitution levels, for example in the US, where again, sexual liberalisation is suggested as the cause. As Norma Ramos, executive director of the Coalition Against Trafficking in Women says "The more the commercial sex industry normalizes this behavior, the more of this behavior you get".

Prostitutes have long plied their trades to the military in many cultures. For example, the British naval port of Portsmouth had a flourishing local sex industry in the 19th century, and until the early 1990s there were large red-light districts near American military bases in the Philippines. The notorious Patpong entertainment district in Bangkok, Thailand, started as an R&R location for US troops serving in the Vietnam War in the early 1970s. Washington D.C. itself had Murder Bay which attracted the military of the Civil War.