WASHINGTON -- A new report indicates that one in every five U.S. jobs pays less than a poverty-level wage for a family of four.

As a result, nearly 39 million Americans, including 20 million children, are members of "low-income working families." That is, families that barely have enough money to cover basic needs like housing, groceries and child care.

The study was published by the nonpartisan Working Poor Families Project, which is a part of the Annie E. Casey Foundation, as well as the Rockefeller Foundation. The report is based on Census Bureau data from 2002 and is to be officially released Tuesday.

The report said federal and state lawmakers should put more money into adult education and job-training programs, increase the minimum wage and expand subsidized child care for low-income parents. Doing so would create more skilled workers who will make more money and, in turn, increase the tax base, the study said.

The official government poverty level depends on the size of the family. For a family of four with two children, the poverty level was income less $18,244 in 2002.

The study looked at working families with kids that earned no more than twice the poverty level. Anyone below that level was considered "low-income." For a family of four, that threshold was $36,488. The median U.S. income for such families is $62,732.

According to the study, about 28 million jobs in the United States provided less than a poverty-level wage, which works out to about $8.84 an hour for a family of four, the study said. The median wage for a waiter was about $6.80 an hour; for a cashier it was $7.41 an hour.