Saturday, August 29, 2009

Infidelity and length of marriage

Males, N = 1,172

Females, N = 1,732

The graphs show the percent of married people who have cheated on their spouse by the number of years they have been married. With the men, prevalence gradually increases up to about 30 years, then goes down perhaps a bit. For the women, the increase is similar but at a lower level, but then there is a collapse after 30 years of marriage.

There is more than one way to interpret the data, but my guess is that: 1) infidelity for both sexes is to some extent a function of opportunity, and the chance that an tempting opportunity presents itself accumulates gradually over the course of a marriage. It's so gradual, people married 30 years are more likely to have cheated than those married 20 years. 2) The drop-off after 30 years is due to fewer unfaithful people among those married before 1960 (the question about infidelity was asked in the early nineties). The decline is not clear for men, but it's dramatic for women.


  1. What happened in 1960 that caused infidelity to go up?

  2. The Sexual Revolution would be my guess.

  3. The Sexual Revoluation would be my guess as well but all the statistics I've read show there wasn't much change in the percentage of people who had premarital sex as a result of the Revolution. I find it strange that extramarital sex is where the largest effect would be seen.

  4. Anonymous8:56 AM

    --What happened in 1960 that caused infidelity to go up?--

    My guess is that greater opportunity leads to greater infidelity. For instance, I normally work from home where I have zero chance to cheat. Recently, I have had to go to an office for work. One cannot help but notice the opportunities for infidelity in a mixed-sex office.

    If you want a faithful spouse, then be sure that they work in a setting not filled with people of the opposite sex.

    My guess is that men and women of the 1800s would have engaged in infidelity at the same rate as today if they were presented with similar circumstances. The power of the libido often overcomes will power.

  5. If you replace years married by age, what happens?

    Things like female fertility and male status are huge drivers of sexual behavior.

  6. The GSS has lots of annoying questions like this where you can't tell what the probability of cheating in the recent past was. That's the most informative.

    As you say, it could be that the "hazard" rate is constant across age, but that those married 30 years have simply had much more time for the event to occur.

    The sexual harassment question is like that too -- "ever" rather than "in the past year." I thought about looking into that as a function of age, but you couldn't tell anything from it given the wording.

  7. Anonymous1:03 AM

    It seems like a lot of variation year to year, possibly noise because the average N per year is necessarily on the small side (N=20 or so per year for the men), with some years probably having a very small N (possibly less than 10).

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