The “half your age plus seven” rule — how often is it broken?

Andrey Kamenov

Andrey Kamenov, Ph.D. Probability and Statistics

When is an age difference between partners a little too large? A common rule is that you cannot date someone younger than half your age plus seven. For example, if you are 30, dating someone 22 years old is just barely acceptable under this rule.

The following chart illustrates this concept: Couples between the dashed lines are the ones following the rule.

Distribution of partners’ ages in unmarried couples

Distributon of partners' ages in unmarried couples

The rule itself, according to Wikipedia, has French origins — but how often is it broken in the U.S.?

Census data on married couples won’t help us much. The (relative) age disparity lessens as both partners grow older. Instead, let’s focus on couples who are living together but are not married yet.

It appears that breaking the rule is getting less and less common. Only 3.6 percent of all couples fall outside the “acceptable” range — compare this to 6.7 percent 10 years ago. Only around a quarter of them are hypergamous, where the woman is older.

Unmarried couples with significant age disparities, 2007-2017

Another interesting fact is that significant age disparities are much less common in Asian couples. The percentage here (2.7 percent of all couples) is only half of the national average. None of the other races exhibited any statistically significant differences.

And of course, it’s interesting to see the difference between states. Here’s the map:

Unmarried couples with significant age disparities by state

Suffice to say, the difference is pretty significant. While numbers around 3 percent are registered in Iowa and Vermont, rates in excess of 8 percent can be seen on the map. Examples of such states include Oklahoma and Arkansas.


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About Andrey Kamenov

Andrey Kamenov

Andrey Kamenov, Ph.D. Probability and Statistics

Andrey Kamenov is a data scientist working for Advameg Inc. His background includes teaching statistics, stochastic processes and financial mathematics in Moscow State University and working for a hedge fund. His academic interests range from statistical data analysis to optimal stopping theory. Andrey also enjoys his hobbies of photography, reading and powerlifting.

Other posts by Andrey Kamenov:

3 thoughts on “The “half your age plus seven” rule — how often is it broken?”

  1. I have never heard of this rule in the U.S. (and I’ve asked others here and they have no idea what rule you were referring to either) so I guess this is or once was a French or European cultural norm.
    To us here, the rule itself would seem problematic in the minds of most of us – even if we didn’t say it out loud. The reason is because it would be incredibly awkward for a man of 40, who has a child who is 20 yrs old to be involved with a 27 year old woman because in that case his child would be closer to his girlfriend’s age than he would be!

    In most parts of the U.S., the acceptable (meaning less cringeworthy) age difference rule seems to be;
    Difference between the ages of father and child
    divided by 2
    then add the result to the child’s age
    and that’s the youngest that man should date.

    So using the example above with the 40 year old man with the 20 year old child, it would be;
    20 years difference between father and child (20/2 = 10)
    Add 10 to the child’s age (20+10=30)
    So the youngest that would be appropriate for the Dad to date would be a 30 year old.
    That has always seemed (to me at least) to be the safest bet.

  2. This rule may have applied to our parents/grandparents time.
    Many females may have boyfriends around their own age but they also have much older sugar daddies. It’s too expensive to not have one. Not many people are getting married anymore. Most females are single mommies and have help with food stamps, HUD housing, etc so there isn’t an incentive to get married. As of 2020 age, race, and even gender disparities no longer matter for many. If you don’t see it yet in your town, you soon will.

    1. “Most females are single mommies”? Where do you get you statistical data? This rule (better term is guideline) is sensible because large age disparities bring its own set of problems. The few young woman you have “suggar daddies” is not a relatinship or marriage. They often have their own close-age boyfriend on the side. One has to look to the future as well. Though there are no guarantees, age disparities can create early widows or leave one partner as a caregiver for many years.

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