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How to Write Percents

Should you use the word or symbol? Is "percent" singular or plural?

By
Mignon Fogarty,
Episode #101

Web Bonus: Using the Word Percentage

It's a little more complicated with the word percentage. The same rules I just told you apply when you are talking about a percentage of something: singular something, singular verb; plural something, plural verb. But when you are talking about the percentage of something, then it is always singular (6).

A percentage of the chocolate chips were missing.

The percentage of chocolate chips missing was shocking.

Also, for percentage, the order of the sentence matters. If the percentage phrase comes later in the sentence, you need a singular verb (2).

A percentage of the chocolate chips were missing.

There is a large percentage of chocolate chips missing.

Words or Symbols

So now that you know how to use percents, let's talk about how to write percents in a sentence. Unlike what I told you last week for the general rules about writing numbers, for percentages it's better to use the numeral and not the word, even if it's a number less than 10. If you're writing about the 5% of chocolate chips that were damaged, use the numeral 5 and not the word five. The only time you would write out the word instead of using the number is if the number was at the beginning of the sentence. Then the rule about not starting a sentence with a numeral takes precedence and you write out the word (7, 8,9). [Note, some style guides disagree and say you can use the word or the numeral when writing out percents (10).]

Next you have to decide whether to use percent the word or percent the symbol. This is kind of like the general rule about writing numbers. If you're writing a technical or scientific document, then most sources recommend that you use the symbol. If you are writing something where numbers are used less frequently, then it is more common to write the word percent. Ultimately, it's a style issue, so make a decision and stick with it. Just remember to use the numeral and not the word for the number.

Decimals

If you're talking about a percent that is less than one, make sure you put a zero before the decimal point. Write something like 0.2%, not just .2%. This is true for writing any numeral that is less than one whether it's a percent or not (10, 11). That little decimal point is too easy to miss without the zero in front of it.

Lies, D*** Lies, and Percentages

Finally, there are a couple of things you should know about calculating and interpreting percentages.

First, something can't decrease by more than 100%. Once 100% of something is gone, there isn't anything left. Never write that a price or anything else decreased by 150%. It's impossible*.

Second, when you are reading about medical, political, or financial news it is important to understand that big percentages can mean small overall increases or decreases. For example, an article that reports a 50% increase in the rate of a rare disease may be telling you that instead of 1 in 100,000 people getting floogety flork disease every year, now 1.5 people in 100,000 get the disease every year. A 50% increase sounds a lot scarier than the increase in raw numbers. Percentages aren't always misleading, but it's something to watch out for.


References

1. percent. Dictionary.com. Dictionary.com Unabridged (v 1.1). Random House, Inc., http://dictionary.reference.com/browse/percent (accessed April 3, 2008).
2. Garner, B. Garner's Modern American Usage. Oxford: Oxford University Press, 2003, p. 598.
3. Wikipedia Contributors. ed. Nygaard, G. Wikipedia: Manual of Style, http://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style_(spelling) (accessed April 3, 2008).
4. Brians, P. "percent, per-cent," Common Errors in English Usage, http://www.wsu.edu/~brians/errors/percent1.html (accessed April 3, 2008).
5. percent. The American Heritage Book of English Usage. Houghton Mifflin Company, 1996, http://www.bartleby.com/64/C003/0227.html (accessed April 3, 2008).
6. percentage. Dictionary.com. The American Heritage® Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004, http://dictionary.reference.com/browse/percentage (accessed April 3, 2008).
7. "Numbers," The Chicago Manual of Style, Chicago: The University of Chicago Press, 2006, section 9 (accessed March 25, 2008).
8. Aaron, J. The Little, Brown Essential Handbook. New York: Pearson Education, 2006, p. 101.
9. Goldstein, N., ed. The Associated Press Stylebook and Libel Manual. Reading: Perseus Books, 1998, p. 156.
10. Lutz, G. and Stevenson, D. Grammar Desk Reference. Cincinnati: Writer's Digest Books, 2005, p. 321.
11. Burchfield, R.W., ed. The New Fowler's Modern English Usage. Third edition. New York: Oxford, 1996, p. 535.

 
 * Sigh. I should know better than to use absolute words like impossible. People have almost convinced me that when a value can become negative, it is possible for the value to decrease by more than 100%. What do you think? Join the discussion in the comments.

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