The Washington Post  

Seven percent of all American adults believe that chocolate milk comes from brown cows, according to a nationally representative online survey commissioned by the Innovation Center of U.S. Dairy.
If you do the math, that works out to 16.4 million misinformed, milk-drinking people. The equivalent of the population of Pennsylvania (and then some!) does not know that chocolate milk is milk, cocoa and sugar.

But while the survey has attracted snorts and jeers from some corners — “um, guys, [milk] comes from cows — and not just the brown kind,” snarked Food & Wine — the most surprising thing about this figure may actually be that it isn’t higher.