Job-based health insurance — the main way Americans get coverage — fell for the fifth consecutive year in 2005, helping push the overall percentage of Americans without health insurance up to 15.9 percent of the population.

Figures released this week by the Census Bureau show that 46.6 million people were without health insurance in 2005, up from 45.3 million in 2004. Unlike in other recent years, there was no increase in the rate of enrollment in government-based programs, such as Medicaid, which had helped to offset declines in private insurance.

The continued decline in job-based insurance comes amid rising health insurance premiums, up about 9 percent in 2005, a smaller increase than in several previous years, but still three times inflation. Many benefit analysts and economists predict that rates for insurance will continue to rise faster than inflation.

"It's especially worrisome because if we get into another economic downturn, there will be even fewer people with access to employer coverage or fewer who can afford it," says Peter Cunningham, senior fellow at the Center for Studying Health System Change, a Washington, D.C., research group.

Even the percentage of children without coverage grew last year, from 10.8 percent to 11.2 percent, ending what had been one of the few bright spots in the effort to decrease the number of people without health coverage.

"This really represents the first increase in the percent of children who are uninsured since 1998," when the State Children's Health Insurance Program went into effect, says Cunningham.

Reasons for the decline in job-based coverage are many, including people losing jobs, employers not offering insurance and workers choosing not to enroll.

The percentage of people who received health insurance through their jobs decreased from 59.8 percent in 2004 to 59.5 percent, the Census figures show. People who bought insurance on their own also fell, from 9.3 percent of the population to 9.1 percent.

In Hawai'i, the state's Prepaid Health Care Act, requires companies to provide health insurance for employers working at least 20 hours a week for four consecutive weeks. Union and government workers are exempt; the government arranges to insure its own workers, while unions negotiate coverage in labor contracts.

Economist Paul Fronstin of the Employee Benefit Research Institute says unemployment may not be low enough to fuel a rise in health insurance rates. The jobless rate fell from 5.5 percent in 2004 to 5.1 percent in 2005 and was 4.8 percent in July.

"The economy hasn't improved enough to have an impact on the uninsured numbers," says Fronstin. "In order to see a turnaround in the number of those who are uninsured, we'll need to see an employment rate in the neighborhood of 4 percent to 4.5 percent."

Employer-based coverage declined in the 1990s, before a brief uptick late in that decade through 2000. Unemployment in 1999 and 2000 hovered around 4 percent, says Fronstin.