Infidelity, Part 1.

Several studies have attempted to look at the causative factors of infidelity.

Sexual Exclusivity among Dating, Cohabiting, and Married Women, Renata Forste and Koray Tanfer, Journal of Marriage and Family, Vol. 58, No. 1 (Feb., 1996), pp. 33-47 was a study of 1,235 women, aged between 20-37, drawn from the 1991 National Survey of Women.

The study aimed to look at infidelity patterns across married, cohabiting and dating groups, with controls for education, age, race, religious value in both the woman and her partner (race of the male was excluded) as well as relationship homogeneity and whether infidelity occurred before or after commencing marriage.

10% of the women of the sample group had a "secondary" concurrent sexual partner. The breakdown was as follows:

Married: 4% had a secondary sexual partner.
Cohabiting: 20% had a secondary sexual partner.
Dating: 18% had a secondary sexual partner.

When analysed across all three groups, the statistically significant--(p<.o5)--findings of this study were as follows: Mainline religion roughly halved the odds. Length of marriage increased the odds. Being married to a 3+ year older man increased the odds. Being in an educationally hypogamous relationship increased the odds. A woman with 1-3 partners was roughly four times(p<.o1), and a woman with 4 or more partners 8.5 times(p<.001), more likely to have a secondary sex partner than a woman with no other previous sexual partners.
From Forste and Tanfer;

Neither the respondents' nor the partners' education alone had an independent effect on sexual monogamy for married women. Statistical significance for respondents' and partners' education among married women was reached only when the educational homogamy measure was added tothe model. Educational heterogamy, however, had a very dramatic effect on sexual monogamy among married women. When married women were more educated than their husbands, they were significantly more likely to have secondary sex partners than women married to similarly educated men. However, if the husband had more education than the wife, the effect was reversed the woman was significantly less likely to have a secondary sex partner than if her education level was similar to her husband's.

After controlling for relationship type, race and ethnicity effects on commitment emerged. Minority race or ethnicity increased the likelihood of having secondary sex partners among dating women and particularly among married women, but race and ethnicity had no effect for cohabiting women. Having previous sex partners also increased the likelihood that dating and married women would have secondary sex partners. In particular, married women with 4 or more previous partners were 20 times more likely to have secondary sex partners than married women with no previous sex partners. The number of previous sex partners had no effect on sexual monogamy among cohabiting women.

Now, I have some reservations with regard to Forste and Tanfer's findings with regard to the marriage findings. There were 603 married women in the study and of those, approximately 4% reported a secondary sex partner. Therefore the conclusions are based on the characteristics of roughly 24 women, a sample size that's pretty small and makes me wonder how much real life significance can be attached to the statistics. The dating group had an 18% secondary sex partner rate in a sample size of 451, i.e approx 81 people, its findings are probably more applicable in the real world.

With that reservation, the table presented below presents a fascinating picture. ( This is an amended table from Forste and Tanfer. Click on image to enlarge)

(Negative odds mean less likely to have secondary partners)

1) The -483 Odds ratio seems difficult to comprehend when it was based on the findings of 24 women. It probably represents the fact that there were no college-degree educated women amongst the married with secondary sexual partners and statistical "magic" conjured the number.

2) The effect of education seems variable. On one hand, it increases the risk of infidelity in dating relationships and yet decreases it in marriage. Women in educationally hypogamous marriages seem to be more prone to infidelity, whilst those in hypergamous relationships seem less likely to seek other partners. It would appear that education is not per se intrinsically protective of infidelity, rather, its protective and corrosive effect seems contextual.

3) Once again, even when controlled for relationship type, increasing numbers of prior sexual partners increase the risk of infidelity.

Forste and Tanfer also looked at the factors which contributed to infidelity both before and after marriage. Once again, this is an amended extract of their report.


Consistently, increasing sexual partner count is associated with a statistically significant increase in odds of infidelity. Even if we exclude the marriage cohort, the promiscuity-infidelity correlation is highly significant.

The Virgin Bride.

Some of the best papers dealing with the subject of sexuality and divorce risk are unfortunately not online. I've purchased a few of these and unfortunately they come with pretty stringent copyright restrictions which means I cannot directly reproduce portions of the document. However I am allowed to comment on them.

One such study was done by Kahn and London. Joan R. Kahn, Kathryn A. London, 'Premarital Sex and the Risk of Divorce', Journal of Marriage and the Family 53 (1991): 845-855.

The data was extracted from the 1988 National Survey of Family group and involved over 2700 white women.

Virginity was defined as having sex within one month of date of marriage. (including before)

Some interesting findings.

At the end of the "Swinging Sixties" some 43% of white brides were virgins. I found this figure quite interesting since the impression that one gets from the media is that everyone was doing it, they weren't

By the early 80's only 14% of white brides were virgins.

In the first part of the paper they undertook a fairly conventional statistical analysis of virginity and its relation of divorce.

They did a probit analysis based on three models:

1) A simple virginity divorce correlation.
2) A virginity divorce correlation controlled for education, age of marriage , marital and per-marital birth.
3) A virginity divorce correlation controlling for all of the above and for intact/non-intact family background and religion.

The above analysis was calculated for 5 year and 10 year divorce risk respectively:

5 year divorce risk for virgins. -0.60. In other words, there was a 60% less risk of divorce.
10 year divorce risk for virgins. -0.402, less than 40% risk of divorce.

The other statistically significant findings were that:

1) Education and age of marriage is negatively correlated with divorce.
2) Education and age of marriage explained about 8-10% of the effect.
3) Coming from a broken home raised the risk of divorce but only for the first five years of marriage. Aat the 10 year mark, it, and age of marriage weren't significant.

The other really surprising finding was that there is no difference in the rate of divorce between Catholics, Protestants and non-religious when controlled for virginity.

The weakest part of the paper came next when they tried to explain the virginity effect by controlling for "unknown" factors using a bivariate probit analysis. Once controlling for these "known unknown" factors, no difference in divorce rates were observed between virgins and non-virgins. Kahn and London then go on to speculate as to what these known unknowns were. They freely admit that they're guessing. They suggested that it could reside in the attitudes and values of virgins compared to non-virgins. Though they admit it would require a study matching attitudes to divorce rates and virginity which they felt would be unfeasible. Essentially, their conclusion is that there is a qualitative difference between virgins and non-virgins which explains their lesser risk of divorce. They did not think that virginity per se was a protective mechanism with regard to divorce risk, rather that some unknown factors associated with virginity are responsible.


Some personal thoughts.

1) We are beginning to see some consistency. Teachman, on a different cohort, demonstrated a 35% reduction in the risk of divorce associated with virginity across cohorts. Kahn and London on a different group demonstrated a similar finding, a reduction between 40-60%.

2) Personally I find Kahn and London's explanation lacking. Their own research in a way repudiates their speculations. A persons religion or lack thereof is probably one of the biggest shapers of their life attitudes. Their own research showed the virginity effect persisted across all believing groups. Teachman was also able to show that cohabitors, who do have different attitudes to non-cohabitors, have no different rate of divorce when controlled for a single partner. Kahn and London showed that religion didn't matter if you were a virgin, whilst Teachman showed that "attitude effect" did not matter if you had premarital sex, only partner count. This explanation is overplayed.

3) Once again, that great shibboleth of the evo-bio crowd, education (which is a proxy for intelligence) had a mild effect on divorce rate, repudiating the haters of the critics of the Heritage Study.

Spend your fifteen bucks and buy a copy of the study.

2002 Male and Female Statistical Data.

I've managed to crunch the numbers from both Male and Female National Survey of Family Growth. As a treat for sdaedalus, I've included the male data.

Method.

First My approach to analysis was Catholic, in that you're only allowed to get married once. Remarriages count as a fail. However the data from NSFG 2002 included remarriages amongst the currently married.

Amongst males, 21% of the currently married were second or later marriages.
Amongst females, 23% of the currently married were second or later marriages.


What I basically attempted to do was calculate the following:

%Married=%married/(%married+%divorced+%remarried) for each sexual partner cohort.

1) The first thing to work out was how many remarriages there were.
2) Then I proportionately distributed the remarriages amongst the the greater-than-two-sexual-partner cohorts.
3) Then I subtracted the remarriages from the current marriages in these cohorts to give me a estimate of married once in each group.
4) Then I added the remarriages to the divorce group and performed the above calculation.

Result.

Note, this graph does not measure how long the the subjects had been married, simply their marriage status by partner count.

It's interesting to note that male promiscuity does not seem to affect marital stability as much as female.

Sexual Partner Divorce Risk

Cohabitation, that is "living together" before marriage has been shown to increase the risk of subsequent divorce of a couple. Many investigators have felt that the practice of cohabitation is selective for people who don't value marriage highly and hence are more likely to divorce when stress is put onto the marriage. In essence, it was thought that the cohabitors more "liberal values" placed them at higher risk of divorce.

Jay Teachman, an academic, investigated this matter further. The study, which is available online, makes for interesting reading. Teachman's genius was to look stratify the cohabitors risk of divorce by the by the number of sexual partners/cohabiting history.

The study was based on data from the National Survey of Family Growth 1995 cycle and involved over 6500 women.

It was controlled for a host of variables.

The study was in no way sponsored or funded by any conservative organisation.

Teachman's conclusion:

The results presented in this article replicate findings from previous research: Women who cohabit prior to marriage or who have premarital sex have an increased likelihood of marital disruption. Considering the joint effects of premarital cohabitation and premarital sex, as well as histories of premarital relationships, extends previous research. The most salient finding from this analysis is that women whose intimate premarital relationships are limited to their husbands—either premarital sex alone or premarital cohabitation—do not experience an increased risk of divorce. It is only women who have more than one intimate premarital relationship who have an elevated risk of marital disruption. This effect is strongest for women who have multiple premarital coresidental unions. These findings are consistent with the notion that premarital sex and cohabitation have become part of the normal courtship pattern in the United States. They do not indicate selectivity on characteristics linked to the risk of divorce and do not provide couples with experiences that lessen the stability of marriage.

Executive summary: It's not the liberal values, it's the number of partners that matter.

And,

This limitation notwithstanding, the results presented here should shift attention away from research that focuses on the selection of individuals into cohabitation and premarital sex to a focus on the selection of individuals who do not marry the individuals with whom they first cohabit or initiate first sex. It may well be the case that, irrespective of the legal status of the relationship, the relevant distinction to make is between people who form multiple relationships and people who form a single, longer lasting relationship.

(My highlighting)

The paper data and methods can be found here. Premarital Sex, Premarital Cohabitation, and the Risk of Subsequent. Marital Dissolution Among Women

Oh, in table 4 of the study, Teachman gives probabilities of divorce, which for fun, we will map onto the Heritage Foundation's study.

10 year divorce rate of the Teachman study group was 34%. (I didn't use the 5 year divorce risk in Teachman's paper since the Heritage study made its calculations on the people being married more than 5 years)

Teachman didn't plot the risk by the number of sexual partners, merely that more than one and in different relationship contexts, so I have simply marked the range of his findings. Note, the really disturbing one still holds. A soon as a woman has had more than one partner her long term marital stability risk drops to near 50%.

Note: Statements reproduced from the Teachman paper are not believed to violate copyright under the fair use clause. Any violation is unintentional and offending material shall be removed immediately if it violates any repespective laws.

Defining Slut: Erratum

I wish to thank commentator R. Stanton Scott for pointing out an error of fact which I had made in the post, Defining Slut.

In that post I stated:

Slut, of course, is the term applied to a promiscuous women and debates rage as to what number of partners earns the title. I think this is the wrong way of looking at the problem. The real danger of a promiscuous woman is that she will be unfaithful, so the definition should be really centered around that concept. i.e How many sexual partners does a woman need to have before she becomes high risk marriage material? The study quoted above asked the question.

The study, Harmful Effects of Early Sexual Activity and Multiple Sexual Partners Among Women, by the Heritage Foundation did nothing of the sort. The study did not look at how many partners a woman needed to have before she became unfaithful, rather the study looked at the number of partners a woman had and her risk of divorce, an important distinction.

The error of fact was unintentional and once again I thank Mr Scott for pointing it out.

Statistical adjustments to promiscuity data.

The Centers for Diseases Control published a document which contained divorce data from the 1995 National Survey of Family Growth. Entitled, Cohabitation, marriage, divorce, and remarriage in the United States, it was able to provide data on divorce probabilities according to individual educational and economic characteristics.

Below are some pertinent extracts to our previous posts. (Click on image to enlarge)


Looking at the table we can see that the average divorce probability is 0.45 after 15 years. If we look at the family income breakdown, we see that the 15 year rate of divorce probability for people earning less than $25,000 is 0.65, an extra 44% risk of divorce above the national average.

Many of the detractors of the Heritage Foundation paper felt that its findings could be explained away by educational/socioeconomic factors. They are wrong.

What's interesting to note, is that ooking at the above table, the risk of divorce varies the most according to economic status. The difference in raw probability from the upper and lower third economic classes is 0.34, whilst the difference between the upper and lower educational categories is 0.23. In real life the two characteristics, income and education, are closely correlated and it would be quite reasonable to assume that the 0.23 subsists within the 0.34. However the Heritage study shows a 0.63 probability variance across cohorts, therefore socioeconomic factors cannot explain all the variation.

However, this 0.34 difference does not apply across the board, it only explains the added socioeconomic risk of divorce on the poor, relative to the rich. Relative to the average (0.43), the poor have an added 0.22 probability. What this means is that poverty increases the risk of divorce compared to the average whilst wealth decreases it compared to the average.

Now, this chart, gives us the socioeconomic and educational breakdown within each sexual-partner cohort.


In order to determine the confounding effect income has on the cohort divorce rate we must sum the weighted risks of each economic group from the cohort and see how it varies from the average.

Example:

If the entire greater-than-10 partner cohort were composed of poor people, we could look at the marital risk chart and see that they have 0.796 probability of divorce(%20.4 are married), we would then subtract 0.22 due to socioeconomic effect, since the the lowest income third have a divorce probability of 0.65, which is 0.22 above the national divorce rate. We know that this increased risk is due to the economic circumstances in which they are in so we subtract that from the 10+ cohort figure to arrive at a figure of 0.576. On the other hand, if the group were composed entirely of the rich, we know that wealth protects against divorce by a probability of 0.12, therefore the adjusted probability would be 0.916.

Using this method we can adjust for income effects in each cohort by determining the cohorts economic divorce risk and comparing how it varies from the average.

% poor x poor divorce probability+%middle x mid divorce probability+% rich x rich divorce probabilty-average divorce probability= adjustment.

The same adjustment can be made for educational status by such a method.
(Click on image for large view)


Explanatory notes:

9.3% of current marriages were remarriages. I distributed these remarriages evenly amongst the 2+ cohorts, any error arising from such is likely to be insignificant in real world terms. Also since I could not control for income and education at the same time, I've presented both corrections. In the real world, income and education are closely correlated so I would not expect to see much variance across the figures however in an effort to capture any socioeconomic/educational affect, the Maximum variant value represents the calculated value which gives the lowest divorce rate. (i.e maximising the impact of socioeconomic/educational factors on these calculations)

What's fascinating to observe, is that the CDC data on cohorts does not generally show a preponderance of one statistical group amongst the others across the partner cohorts. For instance, in the 10+ crowd, there is a slight preponderance of the educated and wealthy over the uneducated and poor, yet the cohort divorce rate for education and income were 0.44 and 0.45 respectively, indicating a variance of 0.01 and 0.02 from the national average. The largest variance was found in the 2 cohort group where 0.03 probability increase of divorce above the national average was predicted due to economic factors.

What this data shows is that sexual partner count is a very good--in fact uncannily good--predictor of the risks of divorce.

How good? One extra partner in a woman is equivalent to negating the protective benefit of greater-than-high school education in a woman, two partners equivalent to having a poverty affected marriage, ten or more partners negates any benefit of income or education with regard to marital risk.

From a statistical perspective, the marital dissolution risk of a woman receiving welfare and a wealthy promiscuous educated woman is about the same.

(This post was revised at 20:00 Australian Eastern Standard Time)