Estimating Number of Lifetime Sexual Partners: Men and Women Do It Differently - Statistical Data Included

Journal of Sex Research, August, 1999 by Norman R. Brown, Robert C. Sinclair

It is common for surveys of sexual behavior to ask respondents to indicate how many sexual partners (SPs) they have had over the course of their lives (e.g., ACSF Investigators, 1992; Johnson, Wadsworth, Wellings, Bradshaw, & Field, 1992; Smith, 1992). Responses to such questions provide important information for epidemiologists and public health researchers concerned with modeling or tracking the transmission of sexually transmitted diseases, and for social scientists interested in characterizing and explicating sexual practices of individuals and groups (Einon, 1994). Of equal importance, such questions provide survey researchers with an opportunity to assess the validity of their instruments (Laumann, Gagnon, Michael, & Michaels, 1994; Lewontin, 1995; Morris, 1993; Smith, 1992). If surveys elicit accurate reports from their respondents, heterosexual men and women should, on average, report having had the same number of partners. This is because each new SP for a man is also a new SP for a woman. Thus, for a closed population, men and women must have the same number of opposite-sex SPs, and therefore should generate similar reports. This, however, is rarely the case. Instead, men typically report two to four times as many opposite-sex partners as women (ACSF Investigators, 1992; Johnson et al., 1992; Laumann et al., 1993; Smith, 1992).

Researchers have attempted to account for these discrepant partner reports in two ways. Good-faith explanations have assumed that respondents answer survey questions as accurately as they can and that the discrepancy reflects biased sampling (e.g., undersampling or failing to sample prostitutes or young female partners; Morris, 1993; Wiederman, 1997). In contrast, bad-faith explanations assume that respondents are "telling themselves and others enormous lies" (Lewontin, 1995, p. 29), with men deliberately inflating their reports and/or women deliberately underreporting. At present, good-faith accounts are considered unlikely because the assumptions required to eliminate the discrepancy seem highly implausible (Laumann et al., 1994; Morris, 1993; Wiederman, 1997).(1) Thus, a consensus has emerged that "intentional misreports are the main source of the discrepancies" (Smith, 1992, p. 210; see also Einon, 1994; Laumann et al., 1994; Lewontin, 1995; Tourangeau & Smith, 1996; but see Wiederman, 1997). If correct, this conclusion has far-reaching implications as it undermines the credibility of self-report data in general, and in so doing suggests that "all scientific sociology ... is in deep trouble" (Lewontin, 1995, p. 24).

The bad-faith explanation assumes that men generally exaggerate their sexual prowess, or women minimize their sexual experiences, or both. If this view is correct, sex-differences should be common across a wide range of sensitive survey questions. However, such differences appear to be more the exception than the rule. For example, men and women typically provide similar responses when asked to estimate the frequency and duration of sexual activity (Laumann et al., 1994), and they are equally likely to acknowledge having engaged in oral and anal sex (Laumann et al., 1994; Tourangeau & Smith, 1996). More importantly, men and women provide very similar reports when asked how many sexual partners they have had in the past year (ACSF investigators, 1992; Johnson et al., 1992; Laumann et al., 1994; Morris, 1993; Smith, 1992).

These findings are inconsistent with the view that people always respond in bad faith when asked about their sexual behavior. At the same time, they raise two interesting questions. First, if people do not, as a matter of course, misrepresent their sexual experiences, what accounts for discrepant reports of lifetime SPs? Second, why is this discrepancy reduced or eliminated when the time frame of the report is narrowed to the past year? In this article, we argue that a strategy-differences explanation can account for both phenomena. This approach takes as its starting point the observations that sexually active people do not necessarily keep a running count of SPs, and that people who have not kept a tally cannot respond simply by retrieving a count from memory. Instead, they must generate a suitable numerical response using one of a variety of potentially applicable estimation strategies.

It is well established that people use multiple strategies to generate numerical estimates, that different strategies are associated with explicable characteristic biases, and that strategy use is influenced by the availability of task-relevant information and the actual magnitude of the to-be-estimated quantity (Blair & Burton, 1987; Brown, 1995, 1997; Burton & Blair, 1991; Conrad, Brown, & Cashman, 1998; Menon, 1993). Of particular relevance, Brown (1995, 1997) demonstrated that people asked to estimate event frequencies sometimes retrieve and count event instances (i.e., enumerate) and sometimes produce rapid intuitive estimates (i.e., rough approximations). Participants who enumerate often underestimate event frequencies because relevant instances may be permanently forgotten, because output interference causes some instances to become temporally inaccessible, and because people sometimes terminate their retrieval efforts before all relevant instances have been recalled. In contrast, participants who produce rough approximations often overestimate event frequencies. It is believed that people generate these estimates by mapping vague quantifiers (e.g., terms like "quite a few," "lots") onto a numerical response scale and that this process produces overestimation because the lower bound of the response scale is anchored but the upper bound is not (Brown, 1995).