A considerable proportion of men worldwide buy sex from female prostitutes, with most estimates of lifetime prevalence ranging from 7 to 39 percent, depending on the country and study. Many experts argue that it is a male appetite-and not the choices of prostitutes-that fundamentally drives the sex trade."

Overall, an estimated 16 percent of men pay for sex in the U.S., according to a 2005 report by social work professor Sven-Axel Månsson of Malmö University in Sweden. And a study published in 2000 of 998 street prostitutes and 83 call girls in Los Angeles led by sociologist Janet Lever of California State University, Los Angeles, suggests that 28 percent of men who patronize prostitutes and nearly half of those who employ call girls buy sex regularly, with the rest being occasional customers.

The proportion of patrons seems to vary considerably by country and by study. Månsson reported that 14 percent of Dutch men have bought sex as compared with nearly 40 percent of men in Spain. (Prostitution is legal in both countries.)

And according to HYDRA, a Berlin-based organization that provides legal advice and other aid to prostitutes, up to three quarters of men in Germany, which also has legalized prostitution, have paid for sexual services. Meanwhile other estimates for Germany put the proportion far lower, at about one fifth. In Thailand, where prostitution is illegal but socially accepted, one study suggested that a whopping 95 percent of men have slept with a prostitute.

Whatever the numbers, the behavior is prevalent enough that psychologists cannot easily write it off as pathological. (...) ("Why Do Men Buy Sex?", Nikolas Westerhoff, Scientific American, December 2008)

Also: "Pimps and patrons : the "boys" in the business", in Roberta Perkins, Working girls : prostitutes, their life and social control, Australia Institute of Criminology, A quote:

"Just as the client views the prostitute as nothing more than a sexual object, so the sex worker feels no obligation to humanise her relations with her customer. Most prostitutes are contemptuous of their clients as men who are cheating on a woman, viz. their wives, fiances, girlfriends. This, coupled with the blatant objectification of prostitutes as women, the base unimaginative lust in most clients, and their folly in paying for sex, are the main reasons for a disdain felt by many prostitutes towards their customers, and is the source for the various terms for them in the prostitutes' argot. "Mug", for instance, among Australian prostitutes has roughly the same meaning as "sucker" in American slang. American prostitutes use the term "trick", alluding to clients' attempts at manipulating for free sex, and also "john" in reference to the clients attempts to conceal their true identity beneath a common pseudonym. English prostitutes call their clients "punters", with the same essential meaning as on the racetrack: that is, they gamble their money away. But these conceptual attempts at providing the prostitutes with a sense of superiority over their clients have an ironic ring. Society, with its male and morality dominated values, perceives the client's interaction with the prostitute as a sex object, his polygynous nature, and his open sexuality as "normal" behaviour, while the prostitutes' promiscuity, economic drive and control over sexual interactions is considered "abnormal". Thus, the client-prostitute relation is complex and contradictory."