Actually, I don't have polling data for you, but I do have this bit from Neil Postman's TECHNOPOLY:

Generally, polling ignores what people know about the subjects they are queried on.  In a culture that is not obsessed with measuring and ranking things, this omission would probably be regarded as bizarre.  But let us imagine what we would think of opinion polls if the questions came in pairs, indicating what people "believe" and what they "know" about the subject. 

If I may make up some figures, let us suppose the following:  "The latest poll indicates that 72 percent of the American public believes we should withdraw economic aid from Nicaragua. 

Of those who expressed this opinion, 28 percent thought Nicaragua was in central Asia, 18 percent thought it was an island near New Zealand, and 27.4 percent believed that 'Africans should help themselves,' obviously confusing Nicaragua with Nigeria.  Moreover, of those polled, 61.8 percent did not know that we give economic aid to Nicaragua, and 23 percent did not know what 'economic aid' means." 

Were pollsters inclined to provide such information, the prestige and power of polling would be considerably reduced.  Perhaps even congressmen, confronted by massive ignorance, would invest their own understandings with greater trust.

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The paragraph breaks are mine, as are any typos.

Enjoy,

herring405