WASHINGTON (AP) _ Surveys for 15 years have shown that men have more sex partners than women, an illogical conclusion that has puzzled experts. New research may explain why: the surveys failed to measure the sexual activity of prostitutes.
``The number of partners that (heterosexual) men have had must be equal to the number of partners that (heterosexual) women have had,″ said Devon D. Brewer of the University of Washington. ``Each new partner for a man is also a new partner for a woman. So, in reality, it must be equal. By definition.″
But the General Social Surveys, conducted by the University of Chicago, and the National Health and Social Life Survey, funded by private foundations, found that men were claiming up to 74 percent more partners than women.
Brewer said social scientists, scrambling to explain this embarrassing inconsistency, suggested one of two basic problems _ survey subjects were lying, or there was some fundamental flaw in the way the data was being collected.
``One explanation was that men are boasting or bragging about their number of partners and that women were being modest,″ said Brewer.
That may be a factor, he said, but a study he co-authored in the Proceedings of the National Academy of Sciences says the biggest cause of the discrepancy is that the surveys ignored the professionals: women who perform sex for profit.
``We found these high activity women, prostitutes, were inadvertently excluded by the design of the surveys,″ said Brewer, whose study appears Tuesday in PNAS.
Brewer said the national surveys sought answers from people who lived in ``households,″ and left out dwellings like jails, motels, shelters and rooming houses where prostitutes are more apt to be.
Also, in order to find people in the households, the surveyors rang doorbells during evening hours, and on weekends and holidays. Although those are the times when most people are at home, but it is also the time when most prostitutes are working, said Brewer.
To test this theory, Brewer and his colleagues analyzed other studies to gain an estimate that there are about 23 prostitutes for every 100,000 people in America.
A second study, Brewer said, concluded that the average prostitute had 694 male partners a year.
``That is an average,″ said Brewer. ``Some have far more and some have far fewer, but that is a representative sample.″
Applying these estimates of prostitute activity to the national surveys put the final numbers for sexual partners about into equal balance between the genders, said Brewer.
Male prostitutes, he said, were not included because ``we believe that is quite rare. There is not a big market out there for women to buy sex from men.″
Tom Smith, director of the General Social Survey at the University of Chicago, said Brewer’s study ``offers a likely explanation for at least part of the discrepancy,″ but that there are also other factors.
Smith said that about 10 percent of the discrepancy may be because the survey did not get responses from sexually active juveniles. This would create a bias, for example, because males over 18 might report sex with young females, but the survey would not include balancing reports from underage girls.
Also, Smith believes that another 10 percent of the bias may come from gender-based attitudes toward sexual surveys.
``We believe there is an overreporting (of sex partners) by men and an underreporting by women,″ said Smith.
The GSS, first published in 1988, is paid for, in part, by the National Science Foundation. Smith said that the Centers for Disease Control and Prevention uses the data to help design and target public health campaigns to control sexually spread diseases.