August 16, 2012
Weekly Language Usage Tips: All about percentages
Tip 1: Percent: singular or plural
A reader writes:
Quick question: The bill directs that 25 percent go to… OR 25 percent goes to…?
The reader is asking whether ‘percent’ is singular or plural. That’s easy. It depends.
Oh, you want to know what it depends on. Okay. Like all collective nouns, ‘percent’ can be either singular or plural; it depends on what it is referring to (in this case, the object of the preposition that follows). If it is referring to a single thing, then a singular verb is used with percent, and if it is referring to multiple things, a plural verb is used. I think it’s easier to demonstrate with examples.
Let’s start with the reader’s examples, but we have to complete the sentence to know whether ‘percent’ is singular or plural.
The bill directs that 25 percent of the money goes to charities.
The bill directs that 25 percent of the prizes go to the local institution.
Does that make it clearer? ‘Money’ is a noncount noun, so we use a singular verb, and ‘prizes’ is plural, so we use the plural verb, ‘go.’ Let’s try one more example.
Thirty-three percent of the study participants were unable to complete the entire survey.
[NOTE: Why did I write out ‘thirty-three’? (And please note the correct use of the hyphen.) It is the first word of the sentence, and the common convention is to spell out the first word. It is also American Medical Association (AMA) style used in many biomedical journals, but you should always check the style guide for your specific journal when submitting a paper.]
Thirty-three percent of the pie was already gone by the time I got to it.
See. ‘Participants’ is plural so we use a plural verb, and ‘pie’ is singular so the verb is, too.
[NOTE: When the number is written out (e.g., thirty-three), then ‘percent’ should be spelled out as well.]
Tip 2: More on percent and percentages
I thought that since we started with ‘percents,’ we should probably cover a few other aspects that can be problematic as well. Like when we should use percent and when we should use percentage.
[NOTE: I am using the AMA Manual of Style as the final arbiter of usage, here, as its rules are followed by many scientific journals.]
We should always use ‘percent’ or ‘%’ when talking about a specific number, and in general, the numeral with the symbol if preferred (e.g., 50%).
[NOTE: When using ‘%,’ there should be NO space between the number and the symbol.]
We found that 28% of the sampled subjects were female and Caucasian.
Of the control group, 40 percent were under the age of thirty.
‘Percentage’ is used as a more general term for a number, and it is a little bit tricky to use. When talking about a percentage, it’s important to have some indication of the size. The use of the number in parentheses helps make the writing more precise. Just saying ‘a percentage’ doesn’t tell us anything; the percentage could be anything from 0% to 100%.
A small percentage (2/50) of the experiments were unable to be replicated.
I am leaving AMA style now, because it is silent on the following, but I wanted to mention this:
When a phrase beginning with ‘of’ follows the word ‘percentage,’ the verb can be singular or plural depending on the word that ‘percentage’ is referring to. For example, in the sentence above, ‘experiments’ is plural, so a plural verb is used.
It is always singular when the verb proceeds the noun. So while:
A large percentage of the fish were swimming upstream.
You would change the verb to its singular form in the following:
There was a large percentage of fish swimming upstream.
When ‘percentage’ is used without an ‘of’ phrase, it is singular unless the number is implied. In the first example, the number is stated in the first sentence, and, thus, implied in the second.
We examined the medical records of 42 patients in our clinic. A significant percentage show no sign of disease.
The percentage is quite high.
Of course this is a very imprecise sentence that we would avoid anyway.
And to make matters worse, according to the American Heritage Dictionary, if you are talking about ‘THE percentage’ rather than ‘A percentage,’ then you use a singular verb, too.
A percentage of the patients are going to be immune to the effects of the drug.
The percentage of patients immune to the effects of the drug is small.
However, it seems to me, that although defined differently, these last two rules are really the same. I don’t think you’d ever use ‘A’ in a sentence where the number is not implied or stated. For example, you would never say:
A percentage is quite high
A percentage of patients immune to the drug’s effects is small.
They both come out the same in the end, so whichever rule you prefer to learn and live by is fine. We still need to talk about percentages and percentage points, but this is a start.