From the Science Daily summary:
Although the nation is spending more on welfare than ever before, most of that money is going to better-off families rather than the very poorest, a researcher found. Researchers found that the United States has become more generous over time in supporting low-income families, spending 74 percent more in inflation-adjusted dollars on welfare programs in 2007 than in 1975. But for the 2.5 million single parent families with the absolute lowest levels of earnings, aid dropped 35 percent between 1983 and 2004. During that same period, aid rose 74 percent for those earning slightly more.
The benefits squeeze: support for some of America’s poorest has dwindled
Source: Lydia DePillis, Washington Post, August 7, 2014