Small bites

Making big numbers more understandable

The wildfires are at it again: One near Colorado Springs was really big.

How big?

CNN said it was about “16,000 acres.” The Associated Press said it was a “22-square-mile fire.”

Both numbers indicate “big,” but, as we’ve written before, readers often can’t make meaningful comparisons using just big numbers like thousands of acres. They need a relationship they can understand. And it’s a journalist’s job to help readers to understand.

At least AP is following (in part) its own style advice on wildfires, promulgated late last year:

Use square miles to describe the size of fires. The fire has burned nearly 4 1/2 square miles of hilly brush land. Use acres only when the fire is less than a square mile. When possible, be descriptive: The fire is the size of Denver.

It would have better served readers if that 15,000 acres (or even 22 square miles) had been related to something readers could more easily visualized: The size of Manhattan, for example, or Bermuda. Better still would be to relate it to a local audience: “The fire is about half the size of the Denver metropolitan area.”

You can use the same technique with other numbers, too. A state budget that allocates $3.4 million for one school district’s enrollment can be broken down to show how much the state is spending on each student: $136 in a district with 25,000 students, or $226 in a district with 15,000.

Breaking large numbers into more digestible bits can also help evaluate how reliable a statistic might be. For example, an article that says “Grand Canyon National Park gets five million visits a year” creates the image of a vague crowd. If you divide that big number by the number of days in a year, you could say that “on an average day, Grand Canyon National Park gets about 14,000 visits.” (Note that “visits” is not the same as “visitors,” since some “visitors” “visit” more than once.) That still sounds like a lot, but someone who has been to the Grand Canyon can relate it to the crowds she saw during her own visit.

But if the article also said that “on a busy summer Sunday, 65,000 people are in Grand Canyon National Park,” some alarm bells might go off: Is attendance on a Sunday really that much more than on an “average” day, even taking into account that the park is pretty much deserted in the winter? (If the total visits figure is divided by only half the year, the daily average is still only about 27,000.) That simple arithmetic can spot a factual error, though you’d still have to find out which number was incorrect: the overall attendance or the Sunday attendance.

Just don’t go overboard with your comparisons. In his entertaining seminar “Afraid of Math? Take a Number,” Richard Holden, the executive director of the Dow Jones News Fund, uses this (outdated) example of what not to do:

The value of Bill Gates’s stock, based on Wednesday’s closing price of $162.625 a share, reached an incredible $81.4 billion. To put that in perspective: That’s 209,357,326 14-ounce tins of Beluga caviar, or 513 Boeing 747s, or nearly the gross domestic product of Israel. In other words, it’s a lot more money than most people can fathom.

As a way to show how meaningless that amount is, most of the examples are meaningless: Few readers can “see” 209 million tins of caviar or 513 large jets. But comparing one man’s wealth to the GDP of a recognizable country can be very effective.

Microsoft stock, by the way, is down to about $34 a share. How rich (or poor) does that make Gates now? You do the math.

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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. Tags: , , , , ,