++Addition++Henry Harpending reminds us that there weren't many changes in educational affinities from 1940 through 2000. Presumably, steady state continues to be the story into the early 21st century.
A recent Pew Research report contained the following graph:
At first blush it might appear as though, contra Charles Murray, assortative mating is actually declining, as more bosses marry their secretaries and more high-powered women pair up with charismatic stay-at-home dads. While the pair rates among dual grads has increased, so has the percentage of people who go to college. Among those in their twenties today, about half will end up in either the "college" (bachelor's or more) or "some college" categories. The percentages of those who attain a high school diploma or less has dropped in the last 50 years as well, but not nearly at the magnitude suggested by the graph.
We need clarifying data on the frequencies of educationally unalike marriages to similarly compare these with the provided figures over time. Irritatingly, Pew doesn't provide as much and delving into primary census data is too daunting a requirement on this amateur's time. As is, the only thing to glean with certainty is that educational increases have occurred. Nothing novel there.
In 1960, 79.6% of married couples involved two people with the same levels of broadly defined educational attainment (high school or less, some college, college graduate). By 2012, this fraction had declined to 59.4%. Again, at face value it appears as though assortative mating is more a thing of the past than of the future. However, If we break a population into three groups and then pair members randomly, we'd expect the lowest frequency of same-group pairings if the groups were split 33.3%-33.3%-33.3% (intragroup pairings an expected 33% of the time). Conversely, we'd expect the highest frequency of same-group pairings if the groups were split 100%-0%-0% (100% intragroup pairings). The past was closer to the latter; the present closer to the former. Consequently, it's difficult to disentangle the genuine changes in (dis)assortative mating and when they're occurring from what is simply an artifice of the measurement approach.
Parenthetically, in checking to see if anyone else had asked Pew about the missing data, I noticed the report's comment thread. I happened to do so not long after listening to the Derb discuss his hope, a la 1984, in the commentariat. The title of the report from which the graph comes is "Record share of wives are more educated than their husbands". The comments include snark along the lines of women needing to be careful what they wish for because unhappiness and underperforming husbands go together; the subjects women major in are not as academically rigorous as the fields men study; after a generation of tilting the scales in favor of women, women now achieve higher average levels of educational attainment than men do; and the like. Not a single comment echoes what is contained in the canon of the Cathedral. Refreshing.