It is not hard to explain why the highly educated are somewhat more disposed to be married than the less educated:
Adults in First Marriages. Figure 3 indicates that the percentage of moderately educated working-age adults who were in first marriages fell 28 percentage points, from 73 percent in the 1970s to 45 percent in the 2000s. This compares to a 17-point drop among highly educated adults and a 28-point drop among the least-educated adults over this same time period. What is particularly striking about Figure 3 is that moderately and highly educated Americans were both just as likely to be married in the 1970s; now, when it comes to their odds of being in an intact marriage, Middle Americans are more likely to resemble the least educated.
Here is my theory. Women are hypergamous and women of the 1990s are just as likely to have college degrees as men. Since they don’t like to marry down, highly educated women will marry highly educated men and less educated women will also marry less well educated men. Highly educated men will also marry less educated women, but highly educated women will NOT marry less educated men. Therefore, we can expect marriage rates to drop as a function of the rate at which women pursue higher education.
If this is the case, then highly educated men should have higher marriage rates than less educated men while less educated women should have higher marriage rates than highly educated women. As it happens, that’s what the statistics indicate. According to a 2003 study, the peak “ever-married” rate for women between the ages of 40 to 44 in 2000 was 90.5% at 12 years of education while for men it was 89.3% at 19 years of education. Which, you will note, indicates that men tend to prefer women with a high school education whereas women prefer men to have as much education as possible.