The figures are contained in a new study by the Urban Institute's Assessing the New Federalism Project, released Thursday by Covering Kids & Families, a Robert Wood Johnson Foundation program.
Researchers said the decline is largely attributed to increased enrollment in the State Children's Health Insurance Program and Medicaid -- public programs providing low-cost and free health coverage for children.
The same survey showed 4 million uninsured children are eligible for the programs but are not yet enrolled.
Foundation CEO Dr. Risa Lavizzo-Mourey said: "With unemployment at its highest level in almost a decade, the number of uninsured children could rise over the next year. That's why we need to redouble our efforts and enroll each and every one of the more than 4 million uninsured children who is eligible for low-cost or free health care coverage today."