A review of a book entitled The Two-Parent Privilege by Melissa S. Kearney makes the point that outcomes for children of two-parent homes are superior. Meanwhile programs to solve the shortfalls of one-parent households are mostly failures.
The review, and one supposes the book, alludes to the underlying cause without dealing with it specifically. Ironically it is an issue about which I lectured some 40 years ago in a slightly different context. The context then was "automation" and the replacement of skilled factory work by "smart" machines. At the time I asked, "What is to become of those who held skilled factory jobs and thereby made decent livings? Where will they work?"
At a later time the issue was "exporting" manufacturing jobs overseas to low wage places like China and Honduras, and I again asked "What is to become of those men and women who held our manufacturing jobs and made a living when those jobs no longer exist here? The people who did those jobs are still here, but the jobs they can do are not."
Much of the lack of "marriageable men" can be blamed on economically rational policies which had quite serious unintended social consequences. It turned out "learn to code" wasn't the answer for those whose skill was manipulating physical "things" with their hands.
We got rid of the jobs they were able and willing to do, because folk in poor countries were willing to do them more cheaply. The jobs went away, the people who did them did not, and we created no suitable replacements to provide meaningful employment and a living wage, in the absence of which they were no longer "marriageable men."
The result has been substance abuse, deaths of despair, a decline in two parent homes, and a situation where 3 out of 20 men of working age are not in the workforce. We've created a society that can only work if, like Lake Wobegon, all the children (and adults) are above average.
Sadly, that is fantasy and the solution is to create a society that has meaningful employment for most people, including most of the half whose intelligence isn't wonderful. We need to reshore our manufacturing and bring those support-a-family jobs home.