Marriage is in trouble. The past half-century has witnessed staggering changes in the makeup of the American family as the number of single-parent households and children born out of wedlock has skyrocketed. The traditional American family structure is crumbling, and no one's sure why. Now everyone from the government to church leaders to intellectuals--on both the right and the left--are pushing marriage, especially among the poor. But can such efforts turn the social tide and make marriage once again the norm? Should the government have a role in such an intimate, private institution? And for those along the margins, why doesn't marriage seem to matter any more? FRONTLINE correspondent and author Alex Kotlowitz explores the biggest demographic mystery of the last half-century and examines the modern marriage movement.