More than 80 percent of the men said the following would deter them: being added to a sex offender register, having your picture and/or name on a billboard or local newspaper, mandatory prison time, having your picture and/or name posted on the Internet or a letter sent to family members.
Only 47 percent of men said a requirement to attend educational services about prostitution would deter them. Farley said she aims to stamp out prostitution in addition to sex trafficking because of the stories she's heard in the 12 years she spent researching prostitution.
"Our non-profit spent 12 years studying women in nine countries on five continents," said Farley who is executive director of the non-profit Prostitution Research & Education. "Women in prostitution, men in prostitution, and transgender people in prostitution all say the same thing. That is harmful to them and they would do anything else if they had the choice." Farley said previous studies show 98 percent of women in prostitution do not enjoy it.
But Ed Laumann, professor of sociology at the University of Chicago, points out that the research in the London study was far from definitive -- the sample of men was small and the responding men were skewed to those who read the newspaper or want to respond to an ad looking for Johns.
Laumann also says that there may never be a universal answer to the question of why men buy prostitutes because the "oldest profession" changes so often depending on time and culture.
For instance, large surveys have showed prostitution in the United States dropped significantly over the last century, while today 1 in 4 men report visiting a prostitute in some parts of southeastern China, according to Laumann.
"The kinds of folks who used prostitution in the modern era are very different than the ones before," Laumann said, speaking of the results of the National Health and Social Life Survey in 1992 which interviewed a random group of 3,432 people. In that survey, which questioned people ages 18-59, about 10 percent of older men reported that their first sexual experience was with a prostitute.
"That goes to zero in the youngest cohort," said Laumann.
The reason, Laumann reasoned, is that the sexual revolution made premarital sex much more accessible. Now young men go to girlfriends for sex and vice versa instead of some young, unmarried people choosing to pay for sex at a local brothel.