Are there really 47 million uninsured Americans?

I'm wondering how solid these numbers are:

On the 47 million people without health insurance point, that too is a statistic where there is less than meets the eye. First, health insurance does not equal health care (there are not just emergency rooms but cash-based clinics, and conversely, a lot of people with insurance don’t get good health care). Second, of that 47 million, 14 million are already eligible for existing programs (Medicare, Medicaid, veterans’ benefits, SCHIP) yet have not enrolled, 9.7 million are not citizens, 9.1 million have household incomes over $75,000 and could but choose not to purchase insurance, and somewhere between 3 and 5 million are uninsured briefly

If we are going to shoot for massive healthcare reform, the first step should not be the drafting of legislation. The first step should be a transparent and comprehensive national study to figure out exactly who does not have access to health insurance. The answer to that question will tell us everything we need to know about constructing some sort of fix. If the numbers I quoted are correct, for example, then we do not need major reform or expensive plans to cover the uninsured.

In any case it strikes me that we are flying blind with regard to healthcare. We have numbers bandied about by the innumerate media and repeated by innumerate politicians and those numbers could potentially be used to reconstruct ~20% of America's GDP.