In previous posts, we established that most well-educated couples (read: four-year college degree or higher) are marrying each other. Plus a good number of individuals with some college or post-secondary training are marrying each other more often than they used to. That's important, because most single-earner households with any education past high school eventually get to the middle class or higher by the time they hit mid-career.
About 62% of American households are headed by someone with training or education past high school, anywhere from a technical certificate to a PhD. Plus a lot of individuals with no more than high school diplomas are reaching the middle class are they move up their career ladders. Takes a few years but a lot of them are getting there. It's the high school leavers, functionally illiterate, and non-English speakers who (for the most part) get left in the dust. And single moms with young children. Overall, though, most American households are doing okay - meaning they have reached or will reach at least the middle-class, which is good enough for me.
I care less about the unequal spread of incomes in any given year than chronic poverty and minimal social mobility over the life span. Does the fact that high achievers are increasingly marrying high achievers make it harder for others to gain traction? Not directly.
However, all this assortative mating contributes to segregation along class lines, as families, friends, co-workers, and neighbors form increasingly homogeneous clusters of people with similar education, income, and norms. For many individuals, less class mixing means less first-hand exposure to success stories, which in turn undermines the confidence, motivation, and perseverance needed to get ahead in the world. In this way, assortative mating has increased inequality.