Today on NPR's Morning Edition I heard Carl Kasell introduce a story by saying "A majority of Russians believes...". Then in the story itself, the reporter said "Ninety percent of Russians believes..."
This just doesn't sound right. I think we should consider "majority" as being plural, and therefore requiring a plural verb, when it is clear that we are talking about more than one person/thing. That is, we would say "a majority of the air *is*...", but "a majority of Russians *are*, not "a majority of Russians is".