Should the Inequality Debate Focus More On Family Structure?

Is the liberal intelligentsia ignoring the fact that the rise of single-parent households over the past half century has been a major driver of inequality? Two researchers argue exactly that in a recent Wall Street Journal op-ed, saying that the lefty world of academics and policy wonks doesn't want to address this fact because they'd rather attack "neoliberalism" and don't want to be seen as siding with social conservatives as they jockey for foundation funding. Nor do they want to deal with the sticky racial dimension of this question. 
That kind of argument is perfect red meat for readers of the WSJ opinion pages. And, to be sure, there's an element of truth here: As I've written often, a key weakness of progressives is that they're so focused on the economic and structural dimensions of society that they fail to think enough about culture and values. Which is too bad, because there's lot of evidence that the rise of extreme capitalism has shaped America's culture and values far more powerfully and negatively than liberalism. 
Otherwise, though, the authors, Michael Moranto and Robert Crouch, are way off here. There's no conspiracy among liberal policy elites to bury the role of changing family structure in driving inequality -- but rather a consensus that these changes have not been nearly as important as rising earning inequality, as well as other economic and political factors. 
Moranto and Crouch claim that foundations aren't interested in the uncomfortable truth about inequality, and that colors everything else. But actually the leading funder of inequality research -- the left-leaning Russell Sage Foundation -- has long been interested in the link between rising family structure and inequality, going back well over a decade, and is actively seeking grant proposals for research on this right now
Moranto and Crouch say that "few researchers" have looked into this link, but there's a substantial track record of scholarly research on this subject going back over two decades. Jason DeParle of the New York Times offers a nice overview here of how various academics have grappled with this supposedly ignored issue in different ways over time.
After sifting through all the studies, DeParle writes that:
Changes in family structure may explain anywhere from 15 to 40 percent of the increased inequality in recent decades. Readers may wonder why there is such a broad range of estimates. It depends on the time period examined, the income rungs examined, and assumptions about how much the absent parent might have brought into the household.
One reason that the focus of inequality research and conversation is now so concentrated on economic and also political factors is that the wide range of these estimates speaks to how tricky it is to nail down hard conclusions on the role of family. Then there is trying to sort through the all-important question of what been driving these changes in family structure to begin with? A number of academics like William Julius Wilson have argued that the breakdown of the traditional family is closely entwined with the same economic changes that have driven rising earnings inequality. More recent scholars have written about the effects of mass incarceration on family formation. 
This is complicated terrain, and with most academics agreeing that family structure is not a dominant driver of inequality, you can see why the spotlight is trained on other culprits. 
One other point: As my colleague Matt Bruenig pointed out here the other day, the United States is the only advanced country where single-parent households are desperately poor. If we had better supports for these Americans, their circumstances wouldn't stand in such sharp contrast to those further up the economic ladder. We'd have both less poverty and less inequality.