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.Merrill Perlman managed copy desks across the newsroom at The New York Times, where she worked for 25 years. Follow her on Twitter at @meperl.