One of my favorite columnists — Robert Samuelson of the Washington Post — has reviewed the latest book by one of my favorite think-tank scholars — Isabel Sawhill of the Brookings Institution. Sawhill’s book is called Generation Unbound, and it examines perhaps the most important social trend of the past half-century: the steady erosion of America’s marriage culture.

The year John F. Kennedy became president, more than 94 percent of all births in the United States occurred within marriage. The year Ronald Reagan entered the White House, the figure was about 81 percent. By the start of the new millennium, it had dropped below 67 percent. Since 2008, it has been below 60 percent (though, encouragingly, it has gone up slightly since hitting an all-time low in 2009).

As a result, fewer and fewer children are being raised in two-parent, married-couple households. “Single-parent families have exploded,” writes Samuelson. “In 1950, they were 7 percent of families with children under 18; by 2013, they were 31 percent. Nor was the shift isolated. The share was 27 percent for whites, 34 percent for Hispanics and 62 percent for African Americans. By harming children’s emotional and intellectual development, the expansion of adult choices may have reduced society’s collective welfare.”

Analysts such as Charles Murray, Kay Hymowitz, Heather Mac Donald, James Heckman, Brad Wilcox, and Robert Lerman — plus many others — have shown how nonmarital childbearing and family breakdown are exacerbating social and economic inequality. After surveying both geographic and demographic variations in intergenerational income mobility, economists from Harvard and UC-Berkeley concluded that “the strongest predictors of upward mobility are measures of family structure such as the fraction of single parents in the area.”

And yet, despite widespread agreement on the need to rebuild America’s marriage culture, experts remain divided over the best strategy. Is the chief problem — as many liberals would argue — a long-term decline in the earning potential of less-skilled workers? In other words, have structural economic changes reduced the supply of “marriageable” men at the lower end of the income scale? Or is the erosion of marriage primarily a cultural phenomenon, and thus resistant to labor-market solutions?

My own view is close to that of Charles Murray: Regardless of which factors — the feminist movement, the sexual revolution, the Great Society welfare state, wage stagnation, etc. — played the biggest role in triggering the collapse of marriage among working-class Americans, “they don’t make much of a difference any more. They have long since been overtaken by transformations in cultural norms.” I fully support proposals such as expanding vocational apprenticeships, enlarging the Child Tax Credit, and eliminating the marriage penalties in means-tested welfare programs — all of which were recommended by a 2012 report from the National Marriage Project and the Institute for American Values. But I also recognize that reviving marriage will require, above all, a massive cultural shift. To quote what Sawhill wrote on the 20th anniversary of Dan Quayle’s famous Murphy Brown speech: “Unless the media, parents and other influential leaders celebrate marriage as the best environment for raising children, the new trend — bringing up baby alone — may be irreversible.”