As a longtime health economist, I almost fell out of my chair when, during the third presidential debate, Sen. John McCain told the audience that "the average cost of a health insurance policy in America today is $5,800."

He continued: "I'll give them [families] $5,000 to take with them wherever they want to go, and this will give them affordability." He seemed to suggest that the average American family could get adequate health insurance for an additional $800 a year.

Try calling up one or more health-insurance companies in your area. Pretend you are part of a family of four without health insurance. Throw in that one of the adults has diabetes, or had a bout with cancer. Then see what kind of health insurance policy - if any - you can get for $5,800 a year.

According to a highly respected annual survey of employer-sponsored health insurance in America, conducted by the Kaiser Family Foundation and the Heath Research Educational Trust, the average annual premium for the type of insurance employers provide is $12,600.

That includes the employer's and employee's contributions to the premium, but not the family's out-of-pocket costs, which have been rising steadily in recent years. According to the Milliman Medical Index, based on millions of privately insured Americans, average medical costs for the typical American family when out-of-pocket spending is included are $15,600.

What kind of coverage, then, could an annual premium of $5,800 get you, even if your whole family were healthy? And what if one or more members had a chronic illness, or had had a bout with cancer?

Sure, an insurer might get the premium down to $5,800 by excluding enough services from coverage (for example, maternity and mental-health care), strictly limiting various types of spending (such as prescription drugs), and imposing a deductible in the thousands upfront and significant co-insurance thereafter. But what kind of insurance would that be?

Most likely, it would be "un-surance." Once seriously ill, you would quickly find yourself paying a lot of money out of pocket.

I am deeply troubled that McCain appears to believe that a mere $5,800 can buy American families the protection they need against the costs of illness - especially as our economy moves into what may be a deep, prolonged recession, and as more and more Americans are laid off from work.

If you are uninsured or fear that you might lose your coverage, go to the candidates' Web sites and carefully check out what they say about their health-insurance proposals. Leave aside any ideological baggage and clichés, such as socialized medicine - which Sen. Barack Obama's plan, based predominantly on government-subsidized private insurance, certainly is not. (Socialized medicine is something like the health system Americans reserve for their veterans.)

And then support the health plan that you believe protects your own family best.

E-mail Uwe Reinhardt at reinhard@princeton.edu.