Q: Which is correct: “Less than five percent of the people came” or “fewer than five percent of the people came”?
A: Strictly speaking, “fewer” should refer to plural nouns (“fewer kittens”) and “less” to singular nouns (“less milk”).
But with percentages (say, “five percent of the people”), the answer isn’t so black and white. I think (and Bryan A. Garner’s Dictionary of Modern American Usage agrees) that in this case “less” is better. To me, “the people” is closer to a collective mass noun than to a collection of individuals counted up. So I’d suggest “less than five percent of the people.”
There are intelligent arguments for “fewer,” but “less” would be my choice, since percentages suggest quantity rather than counted individuals.