By Charles A. Donovan

Britain's Prince William and his betrothed, Kate Middleton, will marry in April at Westminster Abbey, and people around the world will tune in to a rite as old as spring itself.

Lovers of Shakespeare have noted parallels with Henry V: The young Prince William served his nation in arms overseas, and his beloved's name is Kate. Shakespeare's wooing Harry pleads with a demure Kate, daughter of the French king, for a kiss. Attempting to persuade her that it's appropriate, he says, "We are the makers of manners, Kate."

But if there ever were a time when the manners of a nation's upper classes shaped those of the people, that time is not now - at least not here in the United States, where a report from the National Marriage Project at the University of Virginia finds that marriage is disappearing from 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. If they are married, they are less likely to describe themselves as "very happy" and more likely to divorce. Using survey data and correlating earnings with education levels, he concludes that 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. But for those with only a high school diploma, the divorce rate rose from 34 percent to 42 percent - three points shy of the rate among Americans without a high school diploma.

Then there's childbearing. By 2008, just 6 percent of the babies of college-educated mothers were born out of wedlock. Among mothers with only a high school diploma, the rate was 44 percent. Among those who didn't finish high school, it was 54 percent.

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. The Pew Research Center reports that nearly 40 percent of Americans think marriage is obsolete - gone the way of the horse and buggy.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.

We need a sort of Marshall Plan to restore marriage to reduce the extraordinary public expenses that come with fractured families, as well as to increase the number of children who enjoy the benefits that come with being raised by married parents.

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

Will and Kate's nuptials will occur in an ancient sanctuary. But marriages that begin in other ways can endure, too, 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 - 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 wealth, but perhaps they expected more of themselves. Their society expected more of them, too. 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 is made up of a man and a woman who ask one another, "How much can you love me?" Overcoming marriage's disappearing act will require the most generous answer to that query - the kind of love that can make forgetting, and forgiving, possible.

Charles A. Donovan is a senior research fellow at the DeVos Center on Religion and Civil Society at the Heritage Foundation. This was distributed by McClatchy-Tribune Information Services.