There is a little-known movement sweeping across the United States. The movement is "natalism."

All across the industrialized world, birthrates are falling -- in Western Europe, in Canada and in many regions of the United States. People are marrying later and having fewer kids. But spread around this country, and concentrated in certain areas, the natalists defy these trends.

They are having three, four or more kids. Their personal identity is defined by parenthood. They are more spiritually, emotionally and physically invested in their homes than in any other sphere of life, having concluded that parenthood is the most enriching and elevating thing they can do. Very often they have sacrificed pleasures like sophisticated movies, restaurant dining and foreign travel, let alone competitive careers and disposable income, for the sake of their parental calling.

In a world that often makes it hard to raise large families, many are willing to move to find places that are congenial to natalist values. The fastest-growing regions of the country tend to have the highest concentrations of children. Young families move away from what they perceive as disorder, vulgarity and danger and move to places like Douglas County in Colorado (which is the fastest-growing county in the country and has one of the highest concentrations of kids). Some people see these exurbs as sprawling, materialistic wastelands, but many natalists see them as clean, orderly and affordable places where they can nurture children.

If you wanted a one-sentence explanation for the explosive growth of far-flung suburbs, it would be that when people get money, one of the first things they do is use it to try to protect their children from bad influences.