by RonPurewal Tue Jun 17, 2008 3:45 am
this usage is going to boil down to whether you're taking a percentage of something that's countable, in which case the verb should be plural, or uncountable, in which case the verb should be singular.
examples:
15% of the athletes in the contest were using performance-enhancing drugs. --> plural verb, because 'people' is countable
15% of the machine's output was thrown into the scrap pile. --> singular verb, because 'output' is uncountable
with no context, you can't tell. unless you're trying to write out an arithmetic problem - in which the default is singular ("20% of 200 is 40") - you won't ever write a sentence lacking this sort of context, so that's essentially a non-issue.