The Post attributes the declining murder rates to rising incomes, improved law enforcement technology and community relations, and better trauma care (although the number of non-fatal assaults has fallen similarly). But if you go back to the Post from the late 1980s and early 1990s, you would have heard a lot about family structure.
A very early story, from 1985, raised the alarm about an apparent growing epidemic of amoral, violent, black young men:
Such incidents have raised new fears here [in D.C.] and across the country about the growing instability of urban black family structure and the creation of an underclass of young men capable of killing for a warmup jacket or a pair of running shoes. Social scientists, law enforcement officials and community leaders share some of the same theories about the reasons for this kind of homicide among poor black youngsters. They point to the intense desire for material things amid deprivation, easy access to handguns, and the inability of parents—often young, unmarried mothers—to control or instill values in their children.
In 1991, when Health and Human Services Secretary Louis W. Sullivan released a study on homicide trends, he declared:
The collapse of the American family in the past few decades is historically unprecedented in the U.S., and possibly in the world. Nowhere is this trend more apparent than in the black community.... Some argue that the high rate of single parenthood has not adversely affected our children. But, sadly, the research does not bear them out. . . . Study after study has shown that children from single-parent families are five times more likely to be poor and twice as likely to drop out of school. . . . They are also more likely to be involved in criminal activity, to abuse drugs and alcohol, to suffer ill health, and to become trapped in welfare dependency.
Sullivan's solution was a return to a "culture of character," which he described as "a culture in which parents invest time and attention in their children, and the children of a neighborhood; a culture in which children growing up without a father are a small minority."
A 1994 article focusing on the increase in homicide among young people summarized it this way:
At the bottom of all this, people in every section of the juvenile justice system say, is a critical lack of parenting. ... Federal officials estimate that 70 percent of children in juvenile court are from single-parent households. In the last 30 years, the proportion of single mothers has grown from one in 20 to one in four.
Family structure and parenting were not the only explanations offered for the epidemic of murder. There was plenty written about crack cocaine and the drug war turf disputes, the availability of guns, and about poverty and failing schools. But that single-parent theme was quite widespread.