Almost 30 percent of children [in the U.S.] now live in single-parent families, up from 12 percent in 1968. Since poverty rates in single-parent households are roughly five times as high as in two-parent households, this shift has helped keep the poverty rate up; it climbed to 13.2 percent last year. If we had the same fraction of single-parent families today as we had in 1970, the child poverty rate would probably be about 30 percent lower than it is today. Isabel V. Sawhill and Ron Haskins (source, source)
These numbers seem to correspond to intuition. It’s harder for one person to raise children than it is for two. And the risks of ending up in poverty are therefore higher. However, some caution is needed when linking poverty to family structure. Also, perhaps family structure isn’t so much the cause of poverty as its effect. And then there’s the fact that some countries, such as the Nordic European ones, have low marriage rates and high out-of-wedlock birthrates, yet they are much more egalitarian and have lower poverty rates than the U.S. (source). Part of the reason for this is the more generous welfare systems (and higher taxes ) in Nordic countries. Another part is the fact that
in the Nordic countries it’s quite common for committed couples raising children to just not be married. In the US a child whose mother isn’t married is typically growing up without his or her father being present, which isn’t the case in Sweden or Norway. (source)
“Born out of wedlock” doesn’t necessarily imply “single parent”. It’s family structure, and the presence of two parents – not necessarily “biological parents” or parents of a different sex – that helps families and children avoid or escape poverty, not formal or legal marriage status.
Unmarried biological parents in northern Europe are more likely to stay together to raise the kid than married parents in the US. (source)
This quote isn’t intended to imply that unmarried couples are better than married ones. Again, what matters isn’t marriage as such but family structure. And the focus on family structure isn’t intended to imply that all single parents are bad. Even if there’s only one parent, descent into poverty isn’t destiny. It also depends on the parent. Poverty isn’t a mechanical result of a certain family structure, but family structure does count in many cases (a poor single mother, even with the best intentions and efforts, will perhaps do worse than a celebrity divorcee). Having two parents is extremely helpful.
Yet we shouldn’t forget that poverty has many causes and family structure is just one of them, and most likely not the most important one. Hence it’s very well possible that a society with extremely high rates of single parents and births out of wedlock experiences less poverty (including child poverty) than another society where the large majority of children are raised by two biological parents and the large majority of marriages doesn’t break down.
Here‘s a graph indicating that living with only one parent certainly doesn’t condemn children to poverty.