Hanna , I agree with you that declining rates of marriage are the result of largely good shifts in society such as female independence and sexual liberation. I'll add that divorced levels spiked in 1960s-80s, and those of us who grew up in that era are just way more cautious about entering contracts that are so hard to leave if necessary. It's good that people are being freed to think more carefully about the commitments they make. The National Marriage Project that released the study lamenting the decline of marriage in the lower-middle class is a more scrupulous organization than most right-wing think tanks, but it is still are a right-wing think tank and its mission is to restore the patriarchy to a perceived '50s-era heyday. So I take all its conclusions with a grain of salt.
As an obstinately unmarried person who grew up the high-school-educated middle class that NMP and Ross Douthat are condescendingly wringing their hands over, I can say with some confidence that I don't get why anyone cares if marriage is on its way out. It actually makes sense that not marrying is a practice that's moving up the income ladder, probably at the same damn rate that income inequality is spreading. There used to be two reasons to get married: social condemnation of sex outside of marriage and economic stability. Both those are gone as reasons, so why on earth would you add the risk of divorce to your life when you don't have to? Marriage confers no real protections if you don't really have much personal wealth. Nor does it seem like it's necessary if you're both financially independent and capable of keeping your finances separate.
Sure, marriage chauvinists can point to things such as marriage's impact on health and well-being, and to the fact that married men are less anti-social . I'm skeptical, though, because these kinds of studies lump all nonmarried people into one group. People who are in long term, committed relationships without that piece of paper are put in the same group as people who've never held a relationship together. I want to see apples to apples comparisons. How do unmarried people who've been together for five or 10 years hold up next to people who have been together that long but tied the knot in their first year or two together? That people are giving up on marriage doesn't mean they've given up on love or commitment. In fact, many of us believe our commitments are made stronger by the fact that they are only to each other and not to an institution.