Comparison of the various data sources on the incidence of adultery is difficult because of differences in the collection and presentation of data. Even so, results of the few studies we do have are consistent enough to tell us something about trends and to reveal some surprises.
Kinsey and others provided an interesting essay on extramarital sex among males, but very little data. A major reason for this, explained by the authors, was the inability to get adequate representation in the male sample of older married men from upper educational and social levels: “We have every reason for believing that extramarital intercourse is the source of the hesitance of many of the individuals in such groups to cooperate”. Frequency figures given are thus held to be a minimum, the truth perhaps being 10% to 20% higher.
From available data and allowing for the “cover-up,” Kinsey estimated that about half of all married males had intercourse with women other than their wives, at some time while they were married. Age, social level, and religion were important variables for this sample, the first two, especially, introducing some interesting differences. Among lower-level males, 45% of the youngest married cohort reported having had extramarital intercourse, whereas only 27% did so by age forty and not more than 19% by age fifty. On the other hand, among college-level males, the lowest frequencies were found among the youngest group, in which only 15% to 20% had, the incidence increasing steadily to age fifty, when about 27% was having extramarital relations. Kinsey suggested that lower-level males were more likely to have a great deal of premarital intercourse, with some carryover into marriage followed by a slowing down, which he did not attempt to explain, among the older males. By contrast, upper-level males had a history of greater restraint in the premarital years which continued to be characteristic for some years after marriage, loosening up as they grew older. Though not nearly as great as the differences among social levels, a difference was found between church and non-church related males, the more devout having significantly less experience with extramarital sex.
The data for Hunt’s most closely comparable group revealed that only 41% of the males had ever had extramarital sex. Hunt thought that the lifetime accumulative incidence for the entire sample would be somewhat higher, but still not more than 50%, since the data showed no rise after the age of forty-four. Though Hunt found a slight increase among the youngest cohort, it was small compared to the increases in other types of sexual outlets for this group. Likewise, he found little change compared to the Kinsey data for educational level and religion.
Kinsey and others presented much more data on extramarital activity among females than in the earlier volume on males. His female sample, however, had a much higher ratio of previously married to married women, than is the case in the general population. Since previously married women have a much higher incidence of extramarital relations than do women who have been married only once (Bohannon), this had the effect of inflating Kinsey’s figures. When Hunt “rebalanced” Kinsey’s figures to account for this and compared them with his own sample, he concluded that there was no difference in the accumulative incidences up to age forty-five for the two groups. By age forty-five, 20% of Kinsey’s sample had had extramarital intercourse, compared to 18% of Hunt’s sample. Broken down by age groups, however, a remarkable change was found in the group of women below age twenty-five. Whereas only 8% of Kinsey’s group had had such experience, 24% of Hunt’s had. Comparisons between the generations sampled in these two studies, then, suggest that, in spite of widespread beliefs to the contrary, the incidence of extramarital intercourse has changed little if any among male and female groups in general; it has increased slightly among under-twenty-five males, and greatly among under-twenty-five females, bringing them nearly to the level of their male cohorts. Extramarital sex is increasing in the direction of equality, with the greater increase being among females.
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