Various analyses have tried to decipher just who the uninsured are. These are the main conclusions, with the caveat that there is overlap in these numbers:

THE WORKING POOR The Kaiser Family Foundation estimates that about two-thirds of the uninsured  30 million people  earn less than twice the poverty level, or about $44,000 for a family of four. It also estimates that more than 80 percent of the uninsured come from families with full-time or part-time workers. They often cannot get coverage at work or find it too expensive to buy. They surely deserve a helping hand.

THE BETTER OFF About nine million uninsured people, according to census data, come from households with incomes of $75,000 or more. Critics say that is plenty of money for them to buy their own insurance. But many of these people live in “households” that are groups of low-wage roommates or extended families living together. Their combined incomes may reach $75,000, but they cannot pool their resources to buy an insurance policy to cover the whole group.

Still, about 4.7 million uninsured people live in families that earn four times the poverty level  or $88,000 for a family of four  the dividing line that many experts use to define who can afford to buy their own insurance.

Those people who could afford coverage but choose not to buy it ought to be compelled to join the system to lessen the possibility that a serious accident or illness might turn them into charity cases and to help subsidize the coverage of poorer and sicker Americans.

YOUNG ADULTS Some 13 million young adults between the ages of 19 and 29 lack coverage. These are not, for the most part, healthy young professionals making a sensible decision to pay their own minimal medical bills rather than buy insurance that they are unlikely to need. The Kaiser foundation estimates that only 10 percent are college graduates, and only 5 percent have incomes above $60,000 a year, while half have family incomes below $16,000 a year. Many of these younger people would be helped by reform bills that would provide subsidized coverage for the poor and an exchange where individuals can buy cheaper insurance than is now available.

ALREADY ELIGIBLE Some 11 million of the poorest people, mostly low-income children and their parents, are thought to be eligible for public insurance programs but have failed to enroll, either because they do not know they are eligible or are intimidated by the application process. When such people arrive at an emergency room, they are usually enrolled in Medicaid, but meanwhile they have lost out on routine care that could have kept them out of the emergency room. They will presumably be scooped up by the mandate under reform bills that everyone obtain health insurance.

THE UNDERINSURED The Commonwealth Fund estimates that 25 million Americans who had health insurance in 2007 had woefully inadequate policies with high deductibles and restrictions that stuck them with large amounts of uncovered expenses. Many postponed needed treatments or went into debt to pay medical bills.