Editor's note: The following is adapted from the introduction to the new book "Is Marriage for White People: How the African American Marriage Decline Affects Everyone" by Stanford University Law Professor Ralph Richard Banks. For more, visit the website: ismarriageforwhitepeople.com.

On a bitter cold day in January 2009, throngs formed on the National Mall in the predawn darkness, and as the skies lightened the crowd swelled to a million strong. Children atop fathers’ shoulders; old ladies in wheelchairs thankful to have lived to see this day; college students barely old enough to vote; white-collar professionals with rooms at four-star hotels; and blue-collar workers who had journeyed three days by bus—they came from all parts of the nation and all walks of life to join in the making of history.

My family had made the journey as well. Like most people, we had never attended a presidential inauguration. And I was hesitant to go to this one—concerned about the cost, the crowds, our children missing school—but my wife, a woman who by her own admission never cared much for politics, insisted. So from California to D.C., with three young boys in tow, we went.

After the swearing in, we joined thousands of others lining the route for the inaugural parade. No sooner had the presidential limousine appeared, it seemed, than it stopped and its door opened. Into the frigid air emerged our new president and first lady. They held hands and smiled as they walked, waving to the crowd, whispering into each other’s ears, sharing a laugh. They seemed to be having fun. Together.

For all the African Americans who have occupied the spotlight—from Oprah Winfrey to Bill Cosby, Michael Jordan to Tiger Woods, Condoleezza Rice to Colin Powell—virtually none have done so as a couple, much less been as prominent as the president and first lady. Their residency at 1600 Pennsylvania Avenue not only places them at the center of our political life, it embeds them in our cultural imagination. They’re the iconic family with whom we are all called to feel kinship: two accomplished parents, adorable children, a doting grandmother, and—since moving into the most fabled home in the land—a dog. They’re like the Huxtables—only real, and better.

But the captivating image of Barack and Michelle also accentuates a sobering reality. As African Americans, they are extraordinary in the most ordinary way: They are a married couple raising their children together.

Over the past half-century, African-Americans have become the most unmarried people in our nation. By far.

We are the least likely to marry and the most likely to divorce; we maintain fewer committed and enduring relationships than any other group. Not since slavery have black men and women been as unpartnered as we are now.

Although the African-American marriage decline is especially pronounced among the poor, it is apparent as well among the affluent: doctors, lawyers, corporate professionals.

Black women of all socioeconomic classes remain single not because they want to be, but instead because the ranks of black men have been decimated by incarceration, educational failure, and economic disadvantage.

Nearly twice as many black women as men graduate from college. As a result, college-educated black women are more likely than college-educated women of other races to remain unmarried or to wed a less educated man who earns less than they do. Half of college-educated black wives less educated husbands, a gap that makes such relationships more often conflicted and prone to divorce.

Yet black women do not marry men of other races. Black women marry across class lines, but not race lines. They marry down but not out. Thus, they lead the most racially segregated intimate lives of any Americans.

Why? Why, even amidst rising rates of interracial marriage, are black women the least likely to marry out? What are the consequences of the unprecedented rates at which they marry down or remain unmarried?

These are the questions at the heart of my inquiry in my new book, "Is Marriage for White People?" I find the answers in two very different types of evidence.

For more than a year, I traveled the country interviewing scores of professional black women at length about their relationships with men. Their stories, told with courage and candor, are certain to resonate deeply with some readers and to surprise or even shock others.

Before I conducted my first interview, I devoted several years to the study of the black marriage decline. I began, as law professors typically do, with judicial decisions and legislative enactments but soon found myself immersed in history, social science, and government data about the United States population.

Throughout my book, I repeatedly invoke the idea of the relationship market. Although love cannot be bought or sold, the market metaphor highlights two developments that account for the marriage decline.

One is that the rules of the market have changed, so that people marry for different reasons and with different expectations than in earlier eras.

The other development is equally unprecedented: that women have moved ahead economically and educationally as men have begun to fall behind.

Researching this book has been illuminating, indeed liberating. But writing it has been a struggle.

Although the intersection of race and family has been one of my intellectual preoccupations since my undergraduate days more than twenty years ago, and a professional focus since I joined the Stanford Law School faculty more than a decade ago, finding my voice with this project has not been easy. My book confronts some uncomfortable truths about relationships between black men and women.

The book begins with African-Americans, but it does not end with them. The story I tell of African- Americans and marriage may seem exceptional—and in some ways it is—but it is also representative, distinct more in degree than in kind.

Americans of all races are substantially less likely to be married now than their predecessors were a few generations ago. And throughout society, many men are struggling economically, victims of technological change and an increasingly global market for labor.

As a majority of our nation’s college graduates, women are becoming better positioned than men to take advantage of the economic opportunities of the coming decades. And today’s high achieving women are already more likely than ever to marry a man who is either lower earning or less educated than they are.

As particular as the black experience may seem, it implicates readers of all races. The terrain of marriage and intimacy is shifting, for everyone, as never before. Black people are at the center of a social transformation whose reverberations encompass us all.