From US News and World Report:
"Researchers within the Princeton-Brookings report identified several contributing factors to marriage gaps between various classes. For one, there is a smaller pool of "marriageable" men – those with steady, well-paying jobs -- now than there used to be, especially among those with lower education levels.
For example, 82 percent of men ages 25 to 34 were part of the U.S. labor force in 2012, compared with 93 percent in 1960, according to the Pew Research Center. The share of men who are incarcerated also has surged, with black men and those with low levels of education particularly affected.
Economically, the gap between earnings for men and women has narrowed, reducing the budgetary boost a woman could get from marriage and making it less necessary from that standpoint. In 1980, women earned less than 70 percent of what men earned. By 2012, the gap had narrowed to 93 percent."
So Women get married less because they don't *need* men as much, economically. Now they just look for men that they actually like.
And there aren't many of those. So they stay single. Then it's much less of a problem to leave should he becomes a jerk.
On the flip-side, it's almost too bad because marriage is awesome.