Criminal Sentence 196: Five in Five Grammarians

From a magazine article:

"Approximately one in five adults suffer from allergic rhinitis."

Well, five in five grammarians would be allergic to this sentence. "One" is a singular subject. It's a bit tricky when you add a prepositional phrase into the mix: "in five adults." "One in five adults" is still a singular subject, so the verb should be "suffers."