Hans-Peter Blossfeld and the other authors of Who Marries Whom? draw some general conclusions about educational homogamy today:
Schooling matters more now to your subsequent occupation and income than ever before.
Not having a degree closes you out of the next highest social world (though more so in Europe than in the U.S.).
Age-graded schooling, for long years, means that the marriage market for most people is much more age-bound than it used to be.
Schooling is so intensive that it prevents marriage. Graduation from final schooling (or at least from college) marks you as socially fit to marry.
In an era of dual-earner families, for college-educated women marrying an educational equal may be the best strategy to have both a professional career and motherhood.