The Uninsured: Rates By State And Congressional District The Census Bureau reports that 17 percent of the U.S. population under age 65 was without health insurance in 2008. Texas had the highest rate at 26.5 percent, and Florida was second at 24.8 percent. Massachusetts had the lowest uninsurance rate of those under 65 — 4.6 percent. The uninsurance rate for children under 18 ranged from 20.2 percent in Nevada to 2.1 percent in Massachusetts. Most Americans over age 65 have publicly funded Medicare insurance.