Britain's Prince William and his betrothed, Kate Middleton, will marry next April at Westminster Abbey. People around the world will tune in to a rite as old as spring itself. Lovers of Shakespeare note parallels with "Henry V," the Bard's great history play: How the young prince served his nation in arms overseas.

And how the name of his beloved (though she is not at all French) is Kate. Shakespeare's wooing Harry pleads with the demure Kate, daughter of the French king, for a kiss. Things were a bit different then. Harry must persuade the princess that such a liberty is appropriate, not cheap display. "We are the makers of manners, Kate," he tells her.

But if ever there were a time when the manners of a nation's royalty, in wealth if not lineage, shaped those of the people, that time is not now.

Not here in the United States, where a report from the National Marriage Project at the University of Virginia finds that marriage is disappearing in Middle America.

A shocking "marriage gap" has opened between the broad middle and the upper crust since the early 1970s, project director W. Bradford Wilcox writes in the study, "When Marriage Disappears." Wilcox found that Americans with a high school education but no college degree are more likely to become single parents and, if married, less likely to be "very happy" and more likely to divorce. Using survey data and correlating earnings with education levels, he concludes marital indicators are improving for better-off Americans and declining, sometimes sharply, for those of moderate means.

Take divorce. By the 1990s, the divorce rate for highly educated Americans dropped from 22 percent to 19 percent. For those with only a high school diploma, the divorce rate rose from 34 percent to 42 percent - three points shy of Americans without that diploma.

Then there is childbearing outside marriage. By 2008, just 6 percent of babies of college-educated mothers were born out of wedlock, compared with 44 percent for mothers with only a high school diploma.

The unwed birth rate for this middle group soared toward the 54 percent mark for mothers who didn't finish high school.

What Wilcox calls "the retreat from marriage" proceeded during a deep recession and jobless economic recovery. Study after study shows that decisions to marry reinforce male responsibility and promote work. But the dearth of well-paying jobs in Middle America has had an impact. The marriage habit can rust too.

We're in uncharted territory, statistically speaking. Pew Research Center reports that nearly 40 percent of Americans think marriage is obsolete - gone the way of the horse and buggy. But the horse and buggy gave way to superior vehicles. What will replace marriage? Marriage's obsolescence wasn't planned. That doesn't mean it has neither cause nor cure. And a nation that wants to prosper, and see the next generation prosper, must assess those causes and cure as many as possible.

A Marshall Plan to restore marriage, as America invested in a shattered Europe after World War II, would not be too much. But Marshall in reverse, helping reduce the extraordinary public expense of splinting fractured families. It also should increase the number of children who enjoy the benefits of educational attainment and personal success that come with being raised by married parents.

"When Marriage Disappears" also notes that religious attendance is fading in the American middle. An adage, "The family that prays together, stays together," earns fresh support.

It isn't merely symbolic that Will and Kate's nuptials will occur in an ancient sanctuary. But marriages that begin in other ways also can endure, and impart lessons in persistence and faith.

Laura Hillenbrand's new book, "Unbroken," tells the story of Louis Zamperini, a World War II aviator who was lost at sea for 47 days, tortured in captivity and bedeviled by depression and alcoholism.

Restarting a life interrupted and nearly ended by war, Zamperini didn't hesitate - he couldn't wait - to propose to the lovely Cynthia Applewhite when chance brought her into view. Cynthia pledged to help Louis forget his trials. Worried the past ultimately would consume him, he told her: "If you love me enough, I'll have to forget it. How much can you love me?" Economics, welfare policy and cultural norms all count. But so does character. Previous generations had less, but perhaps they expected more - of themselves. Their society expected more of them as well.

As a result, they rose to many an occasion. Will and Kate begin with all the advantages of youth, health, wealth and privilege. Millions of others look upon the prospect of marriage with pasts they might prefer to forget. In the end, every couple - today's Cynthias and Louies among them - is made up of a man and woman who ask one another: "How much can you love me?" Overcoming the disappearing act of marriage in Middle America will require the most generous answer to that query - the kind of love that can make forgetting, and forgiving, possible.