Harold Pollack is a professor at the University of Chicago School of Social Service Administration and Special Correspondent for The Treatment.

The Census Bureau just released its latest income, poverty, and health insurance numbers for 2008. As it reports, the number of uninsured rose by 680,000 between 2007 and 2008, from 45.66 million to about 46.34 million. I’m only relieved things weren’t worse.

Things would have been worse but for one thing: continued expansion of government-provided health insurance coverage. Between 2007 and 2008, the proportion of Americans reporting any private coverage fell by 0.8 percentage points, from 67.5 percent to 66.7 percent. Meanwhile, the percentage reporting some form of government coverage rose by 1.2 points, from 27.8 percent to 29.0 percent.

Unfortunately, the Census Bureau focuses on year-to-year changes. Trends are clarified when one looks over a longer period. The figure below compares government statistics from 1999 and 2008, which show some real trends.

First, the absolute number of uninsured has increased. Second, employer-based coverage is eroding. Third, adverse trends in private coverage are partly masked in the overall numbers by the rise in public coverage.

Fourth, improved insurance coverage among children--thanks largely to Medicaid and SCHIP--is more than offset by increases in the number and proportion of uninsured working-age adults. As shown in the final column, the number of uninsured adults increased by almost 9 million in nine years. Since working-age adults are much more likely to actually get sick, this is a significant economic and public health concern.

None of these four trends is dramatic, but each continues unabated. Democrats and Republicans propose rather different remedies. Yet experts on all sides provide a similar diagnosis. As the costs of health care (and therefore coverage) continue to grow, our traditional employer-based system continues to unravel.

Thank goodness government has been there to (at least partially) fill in the breach.

Update: Ben Smith has more at Politico.