WASHINGTON (AP) -- Children living in single-father households are more likely than those in homes headed by a single mother or a married couple to lack health insurance, a Census Bureau survey found.

The findings puzzled researchers, given that most socio-economic data shows single-mother homes are one of the most impoverished demographic groups. Census Bureau data for 2001 found the median income for a single-mother home is about $22,000, roughly $10,000 less than for single-father homes.

Genevieve Kenney, a researcher at the Urban Institute, a Washington think tank, speculated that many poor single fathers may be unaware of public assistance programs or unwilling to apply for help.

"I'm wondering if single-dad households are just less plugged into public programs," Kenney said.

Specifically, the Census found that kids were uninsured for all of 2001 in just over 20 percent of the 1.5 million families where a single father raised one child, the report found. That compared with 17 percent of 4.5 million single-mother, single-child homes and 10 percent of the 10.3 million comparable married couple homes.

In the 1 million homes where a single father raised two or more children, 17 percent had all children uninsured, compared with 11 percent of the 5 million single-mother homes with two or more kids, and 7 percent of the 17.4 million comparable married couple homes.

The 2000 Census found the number of families led by a man living with one or more of his children, but without a wife, increased 62 percent from 1990, to nearly 2.2 million.

John R. Sims, Jr., president of the Pittsburgh-based Single and Custodial Fathers Network, said too few programs are targeted to those households.

"There is no support for single fathers, absolutely none," Sims said.

The data was part of a Census Bureau report that offered more detailed characteristics of children with and without health insurance in 2001. Findings were based on a national survey of 78,000 households conducted in March 2002.

The bureau previously reported that 9.2 million children, or 12.1 percent of all kids, lacked health coverage for the entire year. The rate had risen over the 1990s to 15.4 percent in 1998, but has declined steadily since then.

The National Center for Health Statistics found a similar decline in a survey it released last year, though it found a smaller number of uninsured kids -- 7.2 million without insurance between January and June of 2002.

Congressional Budget Office analysts in May said that Census Bureau estimates of the uninsured may be overstated because census respondents are asked to report their circumstances during the previous year, but often end up describing their current situation.

Regardless, experts largely attribute the insurance gains to a 1997 federal law that established the state Children's Health Insurance Program, which offers subsidized coverage to more than 5 million kids. The program targets mainly children whose families are not poor enough to qualify for Medicaid, but either can't afford private insurance or work in jobs that don't offer health coverage.

Medicaid covers 30 million people in low-income families, including one in five U.S. children. While most beneficiaries are children and their parents, the bulk of the money is spent on the elderly and disabled.

Most states aren't cutting the number of kids in the CHIP program, though some have frozen enrollments or have eliminated optional coverages, such as for parents, said Leah Oliver, policy specialist with the National Conference of State Legislatures.

"States have been reluctant to cut CHIP," Kenney said. "They are politically very popular."

Another study released last month from the Urban Institute found that 2 million fewer children received health insurance from private insurers between 1999 and 2002, as more companies dropped benefits for workers and their families.

The economic downturn in 2002 and the state budget problems that accompanied it may level off the decline in uninsured children, Kenney said.

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