With the Obamacare exchanges' recent rollout, the rate of people lacking health insurance has shrunk nationally, a trend that many experts say will continue in coming years.
But the strikingly wide differences in the uninsured rates of individual states could become even more pronounced as some governors and legislatures refuse to expand Medicaid eligibility to include more poor adults. As some states add to their Medicaid rolls, other states will not, widening the uninsured gap.
And even Obamacare's looming mandate that larger-sized employers offer affordable health coverage to workers will not erase differences between the insured rates among such employees in different states, observers said.
Having insurance could not only make health-care services more affordable to consumers and lower the "bad debt" that hospitals incur when they treat people who can't pay for those services, but it could also save lives, according to one recent study.
The study, released in May by the Harvard School of Public Health, suggested that lowering the uninsured rate in Massachusetts had lowered the number of preventable deaths in that state by 320 per year. MIT professor Jonathan Gruber argued recently that if Medicaid benefits were expanded nationally, it could save an additional 6,000 lives.
The United States is unique among major Western democracies in its regional insurance-rate differences because of its lack of a national health-care plan, experts said.
"There is pretty huge variation ... between states in terms of their uninsured population," said Jennifer Tolbert, director of state health reform at the Kaiser Family Foundation, the health policy research group.
Nationally, the uninsured rate among non-elderly before Obamacare's launch was 18 percent. It has since fallen to about 13.4 percent, according to recent polls taken after government-run exchanges began enrolling an estimated 8 million people in Affordable Care Act health plans last October.
But Tolbert noted that the uninsured rates—pre-Obamacare launch—had ranged from "27 percent in Texas and Nevada at the highest end" to just "4 percent in Massachusetts." And Massachusetts's uninsured rate has fallen even further, to just about 1 percent, after the launch of Obamacare.
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Kaiser broke out the rates for the non-elderly because nearly all people 65 and over qualify for government-provided Medicare.
Disparity among states' uninsured rates stems from differences in the rates of coverage for specific types of health insurance.
In particular, data shows employer-provided plans and Medicaid account for most of the variation in the overall insured rates of states.
Individual insurance plans have accounted for a relatively small share of states' insurance markets and thus have a smaller effect on the variation seen in uninsured rates between states.