(CNN) - A while ago, my friend told me that a 30 -year -old friend was committed to marry a 50 -year -old person.

The great gap made my mind think of the old woman - and some could argue sexist - "half -seven rule", which has shaped the cultural understanding of what an acceptable age gap is in relations in relationships.

It is a simple mathematical equation that arises more frequently these days in references to relationships involving older men and younger women.The age of the older partner is taken (50 in the previous example), it is divided by two (25) and adds seven (32).If that number is less than or equal to the age of the youngest person in the couple, "the rule" suggests that this person is enough to get the oldest person.And if it is higher, that suggests that the person is too young.

Interpret this "rule" as a strong law of the physics of relationships is something ridiculous and obsolete.Even so, while I explode in my new "Margins of Error" podcast, the differences of age in relationships have been reduced, despite all the press about couples of celebrities with large differences of age.

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— Robot Mowers Mon Sep 07 06:20:29 +0000 2020

In fact, according to data from the US Census Office.UU., the percentage of new marriages between women and men who violate the rule has decreased from 30% to the beginning of the 20th century to a little more than 10% in 1980 to only 3% today.

The decrease in the proportion of people who break "the rule" reflects a society in which women and men are educating themselves better and becoming safer economically.

This has led people (especially women) to marry later.

So how did this supposed rule come about?A deep analysis of the files shows that only in the last 25 years "the rule" came to reflect the minimally acceptable age in a relationship. Solía ​​ser que la mitad de la edad del hombre más siete se consideraba una brecha ideal.

This standard was first launched more than 100 years ago by men, who did not based their statistics findings, but on the dynamics of gender power of the time.According to Economics Professor Terra McKinnish, "the rule" made sense under the male family support model in which "man wants to settle in the labor market to be able to show the income potential.And that's why makes sense...delay marriage a bit to send that signal ".

In essence, social norms demanded that men provide money and women the children.As for contemporary relationships, the data of same -sex male couples tell a different story from that of heterosexual couples.Men in same -sex marriages are much more likely to break the current incarnation of "the rule" than heterosexual couples: 15% compared to that 3% figure that I cited before.

You can find the last episodes of "Margins of Error" in Apple Podcasts, Spotify or your favorite podcast application.