"It left a big hole," said Terri Sterling, a director at the Idaho Community Action Network, a Boise-based organization helping to empower low-income and working Idahoans.
By the Commonwealth Fund's definition, people are underinsured if they have coverage but spend 10 percent or more of their income, or their family income, on out-of-pocket medical care, excluding the premium.
People with very low incomes, below 200 percent of the federal poverty level, are considered underinsured if they spend 5 percent or more of their income on medical care.
In all, 79 million people were uninsured or had inadequate coverage in 2012, prior to the expansion of new health insurance options under the Affordable Care Act, the report found.
Nationally, nearly one in three people (29 percent) was uninsured or underinsured. Massachusetts had the lowest rate of people lacking sufficient coverage or any coverage at all -- 14 percent. The highest rates, at 38 percent, were in Nevada, New Mexico and Texas, followed by Idaho and Florida, at 36 percent.
Four million people, or 13 percent of the total underinsured population, were middle-income, earning between $47,000 and $95,000 for a family of four.
Four out of five underinsured people -- 26 million people in all -- were low-income, earning less than 200 percent of the federal poverty level, or below $47,000 a year for a family of four.
Some good news was noted, too. The number of people lacking any insurance dropped by 2 million to 47 million people in 2010. That improvement is probably the result of a provision of the Affordable Care Act allowing young adults to stay on their parents' health insurance plan, the authors said.