Most journalists didn’t become so because they’re good at math—even economic journalists. But, when dealing with numbers, you don’t have to be a savant to try to make things as clear as possible for readers, most of whom are also not good at math.
Take multipliers—not the straightforward ones, like doubled and tripled, but the fancier ones, like those using “fold” or “as many” or “more.” Because these concepts are tricky, and people have different definitions based on how they were taught, it’s best to be as straightforward as possible. But it’s not easy to be straightforward.
If you have $100, and someone “triples it,” you know you now have $300. (We can dream, can’t we?)
But if your $100 grew “threefold,” how much do you have? (Hint: It’s not $300.) And do you have three times “more” than or three times “as much” as you had before?
SCENARIO A: Take a piece of paper and fold it in half, then in half again, then in half one more time. You’ve made three folds. Now open it and count the squares: You have eight squares. So the $100 that grew “threefold” is now $800.
SCENARIO B: Take another piece of paper and make three accordion folds. Now open it. Voilà! Your three folds yielded four segments. You now have $400.
SCENARIO C: Take your original $100, and multiply it by three. (Did we all get $300? Whew!) Now, add it to your original $100. You now have $400, “three times more” than what you started with.
Are your eyes crossed yet?
The problem is that you think you know what you’re saying, but your readers may understand it differently. Some readers may have learned one of the “fold” techniques in math class; others may have learned the other “fold” technique. Still others were told that “times more than” meant the original quantity plus the multiplier.
If you triple your money to $300 and tell people that you now have “three times as much,” no one will be confused. You had $100; now you have three times what you had before—not “three times more,” but “three times the amount” you had before.
By the way, it doesn’t work in the other direction. You can’t have “three times smaller” or “three times less,” as in “she earned three times less money this year than last.” Once you’ve lost “one,” you’ve lost it all. You can lose only portions of the whole: “She earned two-thirds less money this year than last.”
Stay tuned, and if you’re good, we’ll do algebra next term.

Oh my lord. "-fold" has nothing to do with folding paper, and the meanings that Ms. Perlman assigns to it are completely nonsensical. "-fold" has meant "-times" since Old English (in the form "-feald") and clear back to Anglo-Saxon days and possibly farther: threefold = three times; fourfold = four times; millionfold = a million times.
Seriously, does anyone besides Ms. Perlman interpret "-fold" in either of the ways she describes? Citations?
For what it's worth, none of the dictionaries I consulted even hint at those meanings. (The meaning of "fold" the verb for manipulating paper doesn't seem to have entered the language until well after "-fold/-feald" was well established as a simple multiplier.)
So where does this come from?
#1 Posted by Brian Baresch, CJR on Tue 15 Sep 2009 at 07:46 PM
The first example is, admittedly, far-fetched, but makes the point. I have run across more than a few people who were taught the "fold" method -- incorrectly -- but almost no one who has been taught the etymology of it, so they don't know it's wrong. Pat O'Conner used the "80" example in "Words Fail Me," and on her grammarphobia.com blog: http://tiny.cc/qjBEE
Merrill Perlman
#2 Posted by Merrill Perlman, CJR on Wed 16 Sep 2009 at 07:15 PM
I bought six times as many as I did last week. I know that I bought three last week. Apply the math, and you know that I bought 18 this week.
You say I bought six times more than I did last week, and I am not sure how to apply the math. If I try to fit logic to it I get 21, which is seven times as much.
Math is a science of precision. Well-phrased English can be just as precise and clearly understood.
Unfortunately, our public schools assign literary works that are filled with profanity that is not allowed on television for a fifth-grade class (classKC.org) and don't teach precise language skills anymore.
I have no problem with telling you that I made a six-fold increase in purchases this week as a replacement for telling you that I bought six times as many this week as last. I agree with the first commenter on that point.
However our schools teach the three F's instead of the three R's - Foul mouth, Filthy language and F-bombs.
#3 Posted by Larry K, CJR on Wed 21 Oct 2009 at 04:41 PM
The ratio-based times-more (times-less) usage (six is three times more than two, two is three times less than six) is not uncommon in news stories.
For examples involving AP, AFP, HealthDay and Reuters news stories, see Schield (2010): "Association-Causation Problems in News Stories" at www.statlit.org/pdf/2010SchieldICOTS.pdf
#4 Posted by Milo Schield, CJR on Tue 30 Mar 2010 at 12:17 PM