Charlie, in the comments to this post, refers to a post by Justin Wolfers (who was guest blogging at MR) on the supposed divorce myth. Wolfers argues that the divorce rate is falling, not rising. That may be (though it is hard to measure correctly). But even if it is falling, it may still be higher than it was in 1975. When I last looked at the data, I saw a surge in divorce in the beginning of the 1970s. It probably peaked at some point rather than continuing to rise steadily.
But the more important point is not divorce per se, but the increase in households headed by single moms. They could be single moms because they’re divorced. Could be they never married. But the increase in that category since the 1970s makes it hard to make comparisons across time about inequality.