I see it often claimed that the high rate of child poverty in the U.S. is a function of family composition. According to this view, the reason childhood poverty is so high is that there are too many unmarried parents and single mothers, and those kinds of families face higher rates of poverty. The usual upshot of this claim is that we can't really do much about high rates of childhood poverty, at least insofar as we can't force people to marry and cohabitate and such.
One big problem with this claim is that family composition in the U.S. is not that much different from family composition in the famed low-poverty social democracies of Northern Europe, but they don't have anywhere near the rates of child poverty we have.
A number of studies have tested this family composition theory using cross-country income data and found, again and again, that family composition differences account for very little of the child poverty differences between the US and other countries.
Testing this hypothesis turns out to be really simple. The first thing you do is create a number of family categories. In a 2008 study of this sort, the family categories were: 1) married couple, 2) cohabitating couple, 3) single dad, 4) single mom, and 5) single mom with other adults in the household. The second thing you do is figure out what percentage of all the children live in each kind of family arrangement. The third thing you do is figure out the child poverty rate for each of the family categories (with poverty defined here as families with less than 50 percent of the median income). By multiplying the percentage of children living in each family category by each categories' child poverty rate (and then summing the results), you get the overall child poverty rate.
From there, it is simple enough to just hold the child poverty rates for each family category constant and alter the distribution of children across family types. The following graph is what you get when you use this method to simulate what the U.S. childhood poverty rate would be if children were distributed across the five family categories in exactly the same proportion as children in Finland, Norway, and Sweden are (these being the three countries with the lowest childhood poverty rates):
Holding all else equal, if the family composition of the U.S. matched the family composition of Finland, the child poverty rate in the U.S. would fall from 22 percent to 21.6 percent. If the U.S. had Norway's family composition, the U.S. child poverty rate would increase from 22 percent to 22.9 percent. For Sweden's family composition, it'd increase all the way up to 25 percent. If anything, the family composition of the U.S. is keeping child poverty down somewhat relative to these countries.
The percentage of children being brought up by single mothers (category four) does not differ tremendously between these countries:
What does differ tremendously though is how many of the children growing up in single mother homes are in poverty:
Why the poverty rates differ so much is not mysterious: it's almost entirely about transfers (i.e. welfare programs). You can see this by looking at the poverty rate of children in single parent homes prior to taxes and transfers compared to the same poverty rate after taxes and transfers:
High poverty rates for children in single mother families is a policy choice. In the U.S., we decide in favor of it. In the Nordic social democracies, they decide against it.
Of course, it's not just children in single mother households that have elevated poverty rates in the U.S. The U.S. has massively higher child poverty rates across all family types:
Given the overwhelming size of the category, there are actually more impoverished children in married families in the US than any other family category (at least in this 2000 dataset).
Thus, high child poverty in the U.S. is not caused by some overwhelming crush of single mother parenting. The lowest of the low-poverty countries manage to get along in the world with similar levels of single mother parenting just fine. Morever, relatively high child poverty rates are the rule in every single family type in the U.S., not just some single mother phenomenon. We plunge more than 1 in 5 of our nation's children into poverty because we choose to. It would be easy to dramatically cut that figure, but we'd rather not.