I have not found a direct link to the column, but I suspect that the candidates(Clinton used the same figure) got the figure from the column without looking in depth at the number.Census Bureau data reveal that the uninsured are actually the kind of demographic that consumer product companies dream about. A surprising 85% of the nation's uninsured are currently employed and nearly all have worked in the past year (emphasis mine). They are young -- almost half are between the ages of 18 and 34 -- and nearly three-quarters of the uninsured describe their health as "excellent" or "very good." More than two-thirds have at least some college education and about half earn middle-class incomes.
Interestingly, and you might like this, it appears the 47 million number is in error: CNSNews.com - Obama Falsely Claims There Are 47 Million Uninsured Americans