First, violent crime. Now, teen birth rates. After declining for more than a decade, births to unmarried teenagers suddenly increased 3 percent among 15- to 19-year-old girls between 2005 and 2006, according to the National Center for Health Statistics. Like the uptick in violent crime, this could signal a worrisome trend —- another sign that undesirable social phenomena the nation struggled to curb in the 1990s have begun to ooze back up through the sewer grate. The one-year increase in births to teen moms could be an anomaly. Maybe the numbers for 2007 will show another decline, as adolescent girls...