A key trend in modern society is the rise of assortative mating. It explains so many diffferent things that people complain or worry about.

Briefly and simply what we mean by “assortative mating” is that, to a much greater extent, like is marrying like. No, we’re not making some sly joke about gay marriage here, rather, that looking along many of the different fault lines that divide society, more people are marrying those who are like themselves than used to be the case.

Marriage used to come pretty much from within that group of friends and family that one knew. Maybe from high school even: but things have, as we know, rather changed. We’re all marrying later, we’re more likely to marry someone we met either at work or college, thus we’re more likely to marry someone who has been pre-selected to be like us anyway.

If we marry someone from work, it’s likely that it will be someone who works in the same field as us: so if there is anything genetic that makes one likely to be an engineer, or a nurse, then it’s likely that this whatever it is will be fortified in the next generation. This is pretty much Simon Baron Cohen’s view of the rise in autism. Certain characteristics (roughly measured by our EQSQ personality tests) do indeed make you more likely to be in one job or profession than another and that like marrying like (say, systemisers marrying systemisers) reinforces those traits and thus we get that rise in autism (which he describes as a form of”super systemiser”).

But this isn’t the only such fault line. Assortative mating has also been used to explain the divergence in houshold incomes in the country. We are marrying later, as above and we are meeting out prospective mates at college or work. So we who go to coeelege are choosing our mates from that pool of people who have also gone to college. Or lawyers and other professionals are choosing from a pool of other similar professionals.

Thus we see the rise of the two professional household: and of course its side effect, the rise of the no professional household. This, whatever is happening to individual incomes, whatever is happening to he wage distribution or inequality in general, is going to have a very large effect on the household income distribution.

Further, given that we calculate the inequality rate from household distributions (because that is the way the tax data we use is collected) then it’s highly likely that we will be overstating the effect of economic changes upon inequality, rather than the more social aspects such as assortative mating. As, indeed, many economists try to point out.

What’s prompted all of this is a snippet of information from the TaxProf blog:

A key finding of the report is the partner status of full-time faculty:

• Academic Partner:  36%
• Employed, Non-academic Partner:  36%
• Single:  14%
• Stay-at-Home Partner:  13%

That is assortative mating for you: professors are marrying professors. It’s one thing if, say, someone earning $60 k a year marries someone earning $30k or so: but when there’s two $60k salaries in the same household that’s a household income up in the top 10% straight away. But more importantly, these figures give us an actual number for how prevalent assortative mating is.

There’s nothing wrong with it of course: we certainly wouldn’t want to change people’s behavior either, or even try. But it is a powerful explanation for many of the changes which are going on in society.

About the only divider which I know of which isn’t leading to more such assortative mating is race: there are many, many, more inter-racial marriages than ever before, an excellent outcome as it gives us the hope that the issue of race will, over the generations, simply dissolve away.