The trend is examined in this story, one of the most informative articles on the causes of poverty I've seen in years. It begins:
The reticence was a legacy of the ugly battles that erupted after Daniel Patrick Moynihan, then an assistant labor secretary in the Johnson administration, introduced the idea of a "culture of poverty" to the public in a startling 1965 report. Although Moynihan didn't coin the phrase (that distinction belongs to the anthropologist Oscar Lewis), his description of the urban black family as caught in an inescapable "tangle of pathology" of unmarried mothers and welfare dependency was seen as attributing self-perpetuating moral deficiencies to black people, as if blaming them for their own misfortune.
For more than 40 years, social scientists investigating the causes of poverty have tended to treat cultural explanations like Lord Voldemort: That Which Must Not Be Named.
Moynihan's analysis never lost its appeal to conservative thinkers, whose arguments ultimately succeeded when President Bill Clinton signed a bill in 1996 "ending welfare as we know it." But in the overwhelmingly liberal ranks of academic sociology and anthropology the word "culture" became a live grenade, and the idea that attitudes and behavior patterns kept people poor was shunned.
This is a must-read for its insights and its broader view questions about the causes of poverty that have separated liberals and conservatives, economists and sociologists for years. The story mentions a very interesting experiment conducted in Chicago's Grand Boulevard neighborhood where the Robert Taylor once constituted a miles-long wall of high-rise public housing.