If all states were performing as well as Iowa and 4 other top-ranked states, 4.6 million more U.S. children would have health insurance.

Researchers at the Commonwealth Fund, New York, have published data backing that assertion in a report covering 13 measures of states’ success at providing high-quality health care for children.

Iowa came in first. The other states ranking in the top 5 are Vermont, Vermont, Maine, Massachusetts and New Hampshire.

The 5 lowest-ranked states for children’s health care are Arizona, Louisiana, Mississippi, Florida and Oklahoma.

The 13 performance indicators used include measures representing access to care, quality of care, cost of care, children’s potential to lead healthy lives, and “equity,” or fairness.

The fairness indicators include measures representing how much children’s ability to get care depends on their race or ethnicity, their insurance coverage and their families’ income.

Conditions covered in the report include the percentage of children who were insured, infant mortality rates, vaccination rates, and indicators for variables such as developmental delays and medical treatment outcomes.

The proportion of children who are uninsured ranges from a low of 5% in Michigan to a high of 20% in Texas, the researchers report.

The ratio of children having regular medical and dental preventive care ranges from 75% in Massachusetts down to 46% in Idaho, while the proportion hospitalized for asthma varies from 55 per 100,000 children in Vermont to 314 per 100,000 in South Carolina.