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Why are men reporting more sexual partners than women?


Elina Haavio-Mannila and J.P. Roos, University of Helsinki, Finland


In a recent article in New York Times, The myth the math and sex, Gina Kolata (2007) takes up the well known fact that men and women report widely different numbers of sex partners although this is mathematically impossible.  This result is true all over the world. The discrepancy has been interpreted by referring to evolutionary benefits, norms, attitudes, and status aspirations. According to evolutionary theory, among primates and humans, the ascension to status holds higher reproductive returns for males than it does for females. High status entails greater access to desirable things, in this case, sexual access to women (Jonason 2007; Henrich & Gil-White 2001; Buss 1989). For women the quality of partners is more important because they have a higher level of obligatory investment in their sexual encounters and thus would be wearier about a short-term mating man (Buss & Schmitt 1993; Trivers 1972). Women have more control over their sexual success than men because, according to sexual economics, women are the commodity that men compete over for access (Baumeister  & Vohs 2004).


There are more popular explanations to this discrepancy, too. David Gale, a Berkeley mathematician, remarks in connection to Kolata’s article that he is not just being querulous when he raises the question of logical impossibility. The problem is that when such data are published, with no asterisk next to them saying they can’t be true, they just reinforce the stereotypes of promiscuous males and chaste females. The survey data themselves may be part of the problem. If asked, a man, believing that he should have a lot of partners, may feel compelled to exaggerate, and a woman, believing that she should have few partners, may minimize her past. In this way, the false conclusions people draw from these surveys may have a sort of self-fulfilling prophecy.


This problem is one of the most troublesome issues that self-reporting genreates in sex research (McConaghy, 1999). According to behavioral explanations have focused on how men use prostitutes more often than women, that men start having sex earlier than women, or that men are more sexually assertive than women (Jonason 2007). Some authors have argued that the difference is itself an artifact of reporting biases (Brown & Sinclair, 1999; Wiederman, 1997). For example, men tend to use large round numbers when estimating their sexual success. When participants were told that lie-detection was possible, and assumedly this caused them be honest, the sex difference became negligible (Alexander & Fisher, 2003). Similarly when the question regarding number of sex partners is vague, men tend to report more sex partners because they self-define more acts as sex than women (Sanders & Reinisch, 1999). But these explanations do not address why men would over-report if not otherwise instructed.


Jonason (2007a, b, c) gives psychological explanations. He suggests that men may gauge their own status by comparing themselves to other men in terms of how many sexual partners they have had. In so doing, men who have had more sexual partners appear to have higher status than a man with fewer past sexual partners. In his experimental studies he found that men were more likely than women to use their perceived amount of sexual success as a means of assessing their status. He also showed that men viewed sexual success as more prestigious than women. He suggests that men may be more likely to boost reports about their sex life both in real-life and in surveys as functions of 1) their perception that with more sex comes more prestige and 2) the desire to enhance their perceived status among others.


Statistics on the gender gap in the number of sexual partners


Thanks to the spread of reliable contraceptive methods, it is relatively safe to have sexual experiences with several partners without fear of unwanted pregnancy or sexually transmitted infections. According to a web survey on sexual attitudes and  behaviour (Durex 2005) people around the world have an average number of  nine sexual partners. Men have had more sexual partners than women – 10.2 compared to 6.9.


More scientifically collected data is available from surveys conducted in 1989-2000 in some European countries and United States (Leridon, van Zessen & Hubert 1998; Haavio-Mannila & Kontula 2003; Laumann et al. 1994; Wellings et al. 1994). Among men aged 18-49 years, the highest mean numbers of partners were from The Netherlands (20) and Finland (15) (Table 1). Then came France, Norway, Great Britain and Switzerland (12), and the lowest number was found in Spain (10). Women in The Netherlands, Finland and Norway were reporting 10 partners, Spanish and Swiss women 5 partners, and the lowest numbers, 4, stemmed from France and Great Britain. 


(Table 1).


For four European areas: Sweden, Finland, Estonia and St. Petersburg we have data from a wider age group, 18-74 year olds. The gender difference was smallest, 6.5 partners, in Sweden, and largest in Estonia, 8.3. In Sweden, men had 1.9 times as many partners as women, in St. Petersburg 2.7.



A suggestion to solve the problem


In this article we first show that the gender difference in the reported number of sexual partners in lifetime is restricted to people with numerous sexual partners only. Men and women with a small number of partners report equivalent numbers of partners. Secondly, we examine what is the social and sexual background of the “multiamourous” or polygamic people. Is having multiple partners a socially determined phenomenon or is it a personal, perhaps biological characteristic? 


The gender gap in reported numbers of sex partners has constantly bothered researchers as was discussed above. Clearly men have a tendency to over-report and women to underreport their sexual partners. One possible hypothesis is that men and women have a different definition of what having a sex partner means (eg. as in the case of Clinton-Lewinsky). This is not borne out by the data of the Finnish sex survey, in which the verbal definitions of sexual intercourse given by men and women were identical. Instead, we recently found another explanation.


Inspired by Kolata’s article we checked in our data whether the difference is the same with those who have few partners and those who have many. It is plausible that those who have had few partners remember the number of partners better than those who have had many. But also, those who have had few partners are in a sense “losers”; their potential for producing offspring is lower. Men have a higher pressure than women to have more sexual partners, according to evolutionary theory. The number of partners is directly related to their social position, for instance.  On the other hand, men and women who have had many partners are the “winners” and they have perhaps less pressure to change the reported numbers from the real ones, at least when they are men. On the other hand they have more difficulty to remember the precise number and therefore they might round the number off in the preferred direction. In all our data sets, men tend to report even numbers (5, 10, 20, 30 etc.) much more often than women do.


We hypothesized that those who have had few partners remember the number of partners better than those who have had many. Those with many partners have more difficulty to remember the precise number and would tend to round the number off, with each sex going in the preferred direction. This is coming out from our data from Sweden, Finland, Estonia and St. Petersburg in an interesting way. People who have had fewer than twenty partners have only a negligible difference (1-2) between the numbers of partners reported by men and women. There is no over- or underreporting


(Table 2, Figure 1).



We found that people with fewer than twenty partners, both men and women, reported about five partners. Those who reported having at least twenty partners (15 percent in Sweden and Finland and 10 percent in Estonia and St. Petersburg) accounted for most of  the gender difference: men reported having 46 partners whereas women reported having had only 30 partners. So big a difference cannot be based only on errors in reporting.


One possible hypothesis was that men and women have a different definition of what having a sex partner means (e.g. as in the case of Bill Clinton), but this is not borne out by the data. The verbal definitions of sexual intercourse given by men and women in our Finnish study in 1999 are identical. So the question remains, who is cheating, men or women?


We assume that the men have no reason to over-report the numbers of their life-time sex partners, except for occasional rounding off, whereas women have a very strong interest in underreporting. They should not be seen as being promiscuous. We did a further check controlling for education, under the assumption that it is even more important for highly educated, i.e. more powerful and independent women to under-report. The opposite hypothesis is also possible: women in a power position have no need to underreport. In Sweden and Finland educational groups are more or less similar but the classifications in Estonia and St. Petersburg are so different that we could not use the data.


In Sweden, college education does not predict the number of sexual partners of women, but Swedish men with less education report somewhat more partners than those with higher education (Table 3). In Finland, both men and women with college education report more partners than people with less education.


(Table 3,  Figure 2)


In the less than twenty partners’ group the more educated people have higher number of partners and gender difference is small. It also small among the lower educated Swedes, but in Finland, the less educated women report very few partners and thus the gender difference is large. Corresponding to our opposite hypothesis above, the more educated women in both countries and also the less educated Swedish women have no need to under-report.


In the groups of more than twenty partners, education is related to number of partners in reverse ways. In Sweden, people with less education report many partners whereas in Finland those with more education do so. In both countries, but particularly in Finland, gender differences are smaller among the more than the less educated people. Higher status men need not over-report and higher status women need not under-report the number of partners as much as lower status people tend to do.


In any case, it seems clear that a relatively small minority of men and women are responsible for the difference in misreporting for sex partners and that the number of partners has an important role here.


Who are the people with many partners?


Our second research question is: What kind of people are those who have multiple (20+) sexual partners? We first compare Swedish and Finnish men and women with multiple and few partners as there is more comparable data from these countries. Then we include also Estonia and St. Petersburg for a wider international comparison.


Women with many partners are in both countries younger than those with less than twenty partners whereas men are older (Tables 4-5). People with multiple partners have had their first intercourse at a younger age than the others. They had a slightly more education than the others, and had been married more times. In Finland but not in Sweden, more people with multiple partners than of the others were not married at present. About 80 percent of all study subjects had had sexual intercourse in past month, those with multiple partners slightly more commonly than those with few partners. Achieving orgasm in intercourse was not related to number of partners.


(Tables 4 and 5) 


In Finland, the latest partner of people with many partners had been some other person than their present steady partner. Polyamorous Finns had often read or glanced pornographic books or magazines and watched sex movies. In both countries, women with many partners masturbated significantly more often than other women, but there was no connection between masturbation frequency of men and having many or few partners. Receiving and giving oral sex was typical to people with multiple partners in Finland but not in Sweden, where it was more common. Men and women with many and few partners were equally satisfied with their sexual life as a whole.


Having had multiple partners was connected to sexually liberated and versatile lifestyle, more so in Finland than in Sweden.


Correlation and regression analyses of determinants of numbers of partners in the four areas reveal that in Sweden sexual and social factors do not explain the number of partners as much as elsewhere.  This applies especially to the group of people with at least twenty sexual partners. In this group in Sweden, only male gender explains the high number of partners. Also in St. Petersburg, people with many partners are free-floating men without a special kind of social background.

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