Discussing the art of paring down text and deviations from the original Fog Index formula.

By Meredith L. Dias

Last month, we edited an excerpt from NYTimes.com for our Fog Index column and received several responses from editors who felt that we'd over-edited the sample. These editors raised some intriguing discussion points, so instead of assessing a fresh sample this month, we are going to take another look at last month's sample and review the Fog Index formula that we use.

Our Formula

Generally, we adhere to the Gunning-Mueller Clear Writing Institute Fog Index formula. We don't include two-syllable words with -ed, -es, or -ing suffixes in our percentage of 3+-syllable words. We add this percentage to the average number of words per sentence, multiply by 0.4, and present a whole-number result that has not been rounded.

In earlier times at Editors Only, the late Douglas Mueller of the Gunning-Mueller Clear Writing Institute contributed the monthly article on writing. It was the late Robert Gunning who first articulated the Fog Index, although some sources report that the two developed the index together. We're not sure whether or not this is the case. In any event, the two co-authored How to Take the Fog out of Writing, which has remained the authoritative book on the Fog Index. That book instructs the calculator not to round and to ignore the digits following the decimal point.

When calculation changed from by hand to by computer, some of the nuances of the formula were lost. Ironic, isn't it? The meaning of the formula for simplifying was corrupted by an effort to simplify it.

You can see one instance of variation here. This website contains instructions for writing a Gunning Fog Index computer script. In this case, the scriptwriter is asked to round the final result. The Fog Index formulae here and here include the decimal in the final result.

Last Month's Sample

Last month's sample was particularly challenging, as it conveyed medical information vital to the reader's understanding. But the Fog Index was 20, so we decided to take on the challenge of paring it down. Sentence length (average: 43) contributed heavily to this high score, so we were left with the difficult task of paring down the sample to bring the Fog Score below 12, which Gunning determined to be ideal in his formula.

The Response

Steven Cherry, senior associate editor of IEEE Spectrum, asked us why "engage in the charade of not rounding" our final result, and we wanted to clarify that this is no sleight of hand on our part. When Douglas Mueller wrote the Fog Index column for Editors Only, he used a whole number (not rounded) as the final result. So we have always done the same.

Donald Tepper, editor of PT in Motion magazine, presented an alternate recasting of the sample, which we will include here:

"For instance, many children who had seizures and chronic problems after receiving the whole-cell pertussis vaccine actually had Dravet syndrome, a severe form of epilepsy. That vaccine, which routinely caused fevers in children, is no longer used. However, Congress created the national vaccine injury compensation program to address the flood of lawsuits over the vaccine's effects. Children who had seizures after receiving the vaccine have been among the most well-compensated."

An Editor's Role

Is an editor's job is to be sure that every nuance of the writer is left in the final, edited manuscript? The premise of the Fog Index suggests not. Sometimes, nuance can become unnecessary detail, and that can interfere with the reader's understanding of the primary message. Certainly, though, the defogging should not alter the writer's point of view or introduce inaccuracies into the text.

It was not our intention to eliminate vital information from the sample, but if we did so, perhaps it can serve as a teachable moment. When a Fog Score is particularly high, we need to trim unnecessary words and, in some cases, information. Still, we must be careful. If we're too zealous in our pursuit of an ideal score, we can strip the text of something vital.

Meredith L. Dias is senior editor of Editors Only.

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