The Census Bureau reports that in 2007 nearly 37 million of the uninsured were employment-age adults (ages 18 to 64) and more than 27 million worked at least part-time. Approximately 61% of the roughly 45 million uninsured live in households with incomes under $50,000 (13.5 million below $25,000 and 14.5 million at $25,000 to $49,000). And 38% live in households with incomes of $50,000 or more (8.5 million at $50,000 to $74,999 and 9.1 million at $75,000 or more). As stated by the Census Bureau, people of Hispanic origin were the most affected by being uninsured; nearly a third of Hispanics lack health insurance. In 2004, about 33% of Latinos were uninsured as opposed to 10% of white, non-Latinos However, this rate decreased slightly from 2006 to 2007, from 15.3 to 14.8 million, a decrease of 2 percentage points (34.1% to 32.1%). The state with the highest percentage of uninsured wasTexas (24.1% average for three years, 2004–2006). New Mexico has the second highest percentage of residents without health insurance at 22%.It has been estimated that nearly one-fifth of the uninsured population is able to afford insurance, almost one quarter is eligible for public coverage, and the remaining 56% need financial assistance (8.9% of all Americans). An estimated 5 million of those without health insurance are considered "uninsurable" because of pre-existing conditions. A recent study concluded that 15% of people shopping online for health insurance are considered "uninsurable" because of a pre-existing condition, or for being overweight. This label does not necessarily mean they can never get health insurance, but that they will not qualify for standard individual coverage. People with similar health status can be covered via employer-provided health insurance, Medicare, or Medicaid.

Uninsured children and young adults
The current estimate for uninsured children does not greatly differ from past estimates. In 2009 the Census Bureau states that 10.0 percent or 7.5 million children under the age of 18 were medically uninsured. Children living in poverty are 15.1 percent more likely than other children to be uninsured. The lower the income of a household the more likely it is they are uninsured. In 2009, a household with an annual income of 25,000 or less was only 26.6 percent likely not to have medical insurance and those with an annual income of 75,000 or more were only 9.1 percent unlikely to be insured. According to the Census Bureau, in 2007, there were 8.1 million uninsured children in the US. Nearly 8 million young adults (those aged 18–24), were uninsured, representing 28.1% of their population. Young adults make up the largest age segment of the uninsured, are the most likely to be uninsured, and are one of the fastest growing segments of the uninsured population. They often lose coverage under their parents' health insurance policies or public programs when they reach age 19. Others lose coverage when they graduate from college. Many young adults do not have the kind of stable employment that would provide ongoing access to health insurance. According to the Congressional Budget Office the plan the way it is now would have to cover unmarried dependents under their parents' insurance up to age 26. These changes also affect large employers, including self-insured firms, so that the firm bears the financial responsibility of providing coverage. The only exception to this is policies that were maintained continuously before the enactment of this legislation. Those policies would be grandfathered in.

Non-citizens
Non-citizens are more likely to be uninsured than citizens, with a 43.8% uninsured rate. This is attributable to a higher likelihood of working in a low-wage job that does not offer health benefits, and restrictions on eligibility for public programs. However, most of the uninsured in the US are citizens (78%). The longer a non-citizen immigrant has been in the country, the less likely they are to be uninsured. In 2006, roughly 27% of immigrants entering the country before 1970 were uninsured, compared to 45% of immigrants entering the country in the 1980s and 49% of those entering between 2000 and 2006.

Most uninsured non-citizens are recent immigrants; almost half entered the country between 2000 and 2006, and 36% entered during the 1990s. Foreign-born non-citizens accounted for over 40% of the increase in the uninsured between 1990 and 1998, and over 90% of the increase between 1998 and 2003. One reason for the acceleration after 1998 may be restrictions imposed by the Personal Responsibility and Work Opportunity Reconciliation Act (PRWORA) of 1996. Almost seven out of ten (68%) of uninsured non-citizens live in California, Texas, Florida, or New York.