Seven percent of all American adults believe that chocolate milk comes from brown cows, according to a nationally representative online survey.

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.

Cows tend to produce one colour of milk - that is white. Credit:Karl-Josef Hildenbrand/AP

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.

For decades, observers in agriculture, nutrition and education have griped that many Americans are basically agriculturally illiterate. They don't know where food is grown, how it gets to stores - or even, in the case of chocolate milk, what's in it.