U.S. Census Bureau: Wages and Employment Among the Working Poor: New Evidence from SIPP

… persons aged 18 to 64 years who were in poverty in 1984, approximately 40 percent worked at some point during the year and 3.4 million were the sole or primary wage earner in the family. Among the latter group, about one in four worked year-round but were still unable to move their families out of poverty. …