At least 321,000 Hawai'i residents lacked healthcare insurance at sometime during a two-year period that includes part of 2007, a new report says.

The number constituted 29 percent of the state's population under age 65, according to the report by Families USA, a non-profit group in Washington, D.C. that advocates for high-quality, affordable healthcare for all U.S. citizens.

The state ranked 38th in terms of the percentage of people who were uninsured during the period and was below the national average of almost 35 percent. The national average translates into more than one in three non-elderly people going without health insurance sometime during the two-year period.

Hawai'i's number was up from the 1999-2000 period, when 308,000, or 28 percent of Hawai'i residents under 65, went without healthcare coverage at some point.

Families USA said the national trend shows the consequences of inaction when it comes to expanding health coverage. It said the number of uninsured has risen because health insurance premiums are getting more costly and the changes in the labor market.

"The number of uninsured has reached crisis proportions that must be addressed by the president and Congress to ensure that health coverage is available and affordable for all," said Ron Pollack, executive director of Families USA, in a statement.

Hawai'i fared well when it came to a ranking of states by those where people under 65 went without insurance for six months or more during the two-year period. It found 56 percent of those without health insurance fell into this category. That was the second-lowest percentage nationwide, with only Minnesota doing better.

Hawai'i typically ranks well in such surveys because Hawai'i employers must offer health insurance coverage to full-time workers under the state's 1974 Prepaid Health Care Act.

The state also did well when it came to the percentage of children in families with income that's 200 percent or greater of the federal poverty level and who are enrolled in Medicaid or state Children's Health Insurance Programs. It was one of 29 states where eligibility was extended to children with family incomes of more than 200 percent the poverty level.

The study for Families USA was done by The Lewin Group, which analyzed data from the Census Bureau's Current Population Survey and the Survey of Income and Program Participation.

Reach Greg Wiles at gwiles@honoluluadvertiser.com.