According to US Census Bureau statistics, of the 45 million uninsured in 2003:
-15.3 million had incomes below $25,000
-14.8 million had incomes from $25,000-50,000
-7.2 million had incomes from $50,000-75,000
-7.6 million had incomes above $75,000
This is 24.2% of people whose incomes were under $25,000, versus 8.2% of those with incomes over $75,000.
Of the uninsured between age 18-64, 20.1 million were employed full time, 5.9 million were employed part time, and 9.7 million were not working.
-12.4% of the population was covered by Medicaid and 13.7% by Medicare.
-1.3 million people formerly covered by employer-based insurance lost coverage between 2002 and 2003.
-11.4% of children have no health insurance; 19.2% of children in poverty have no insurance.
I hope that helps.
Source: US Census Bureau report, Income, Poverty, and Health Insurance Coverage In the United States: 2003.