A reporter recently sent me this question:
Which of the following is correct:
“Ten percent of Americans plan to give….”
“Ten percent of Americans plans to give…”
I know the first one sounds better, but I think the second is grammatically correct when you think of “of Americans” as a modifier for “ten percent,” which would be doing the action.
I was pleased to tell her that her instinct was right and that she should use the plural verb plan. I explained that, in this case, the number of the verb is determined by the noun that comes after the preposition, and that the principle at work is synesis, meaning that the sense of the sentence determines the choice of the verb rather than the rules of syntax. This is also called notional agreement. Of course, I could have also directed her to the AP Stylebook’s entry on percent, and I probably should have. Because she seemed to want to dig into the issue, though, I gave her a bit of grammar speak. I hope it sticks.