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I've tried searching Google and StackExchange for this one, but I find it difficult to state the problem generally and therefore have had no luck so far; apologies if the answer is already out there somewhere (and easily to be found given the right formulation).

Now to flesh out the rather abstract phrasing in the title of my question - which of the following (if any) is correct:

(a) The performance of Y and Z is comparable.


(b) The performances of Y and Z are comparable.

My intuition is that both are at least commonly used, and perhaps even correct. But do you know of any grammar book that addresses the issue? And what is your intuition as a native speaker (if applicable)? Please don't argue by saying that (b) is more logical, language as a rule doesn't have to be logical :) I'm interested in a normative body's opinion and/or your native speaker's intuition. (If I were a native speaker myself, I'd use whichever would feel most natural to me, not being overly fond of prescriptive grammar, but I don't have that choice.) Thank you!

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I (UK native) would use (b). Two performances, therefore use the plural. – Mynamite May 27 '13 at 11:59
thanks for pitching in :) – dlukes May 27 '13 at 15:49
up vote 0 down vote accepted

Personally, I'd normally use a third permutation...

(c) The performance of Y and Z are comparable.

...but obviously as OP has already discovered, all variations occur. Only a pedant would say that one form is inherently "right" and the others are all "wrong". Consider, for example,...

"The top speed of your car and mine are the same, but mine accelerates from 0-60 mph faster".

I suggest that structurally this is the same as OP's example, but very few speakers would use is there instead of are. And I think most people wouldn't pluralise top speeds either.

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this is a very helpful discussion of the issue, I'd vote it up if I had enough reputation :) I'll wait a bit to see if anyone digs up a reference to a grammar book (the other part of my question), since it might be useful for other people facing the same question to have that as the accepted answer, but if not, I'll accept yours. thanks! – dlukes May 27 '13 at 15:43
@dafydd.lukes: It's very difficult for me to find statistically significant evidence of actual usage - but as I say, quoting grammar books in an attempt to rule any particular form in or out is just pointless pedantry. For what it's worth though, you might note that according to Google's "guesstimated" results, "price of gasoline and diesel are" occurs twice as often as "prices of gasoline and diesel are", but "price of gasoline and diesel is" is more common than either of those. IMHO, none are inherently "right" or "wrong", though. – FumbleFingers May 27 '13 at 16:11

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