The average sentence length is arguably the best indicator of text difficulty. A writer who uses this yardstick has to divide the number of words by the number of sentences. If we choose a sample of 10 sentences, then the calculation becomes simpler. “Sentences in Time and Reader’s Digest vary considerably in length, but the average sentence length, issue after issue, is only about 17 words,” writes Robert Gunning in How To Take The Fog Out Of Writing.
If our writing measures up to this standard, then in 10 sentences there may be about 170 words. Too much of counting, you say? I have solved this problem with the help of a short sample of words, a count of complete sentences and a simple scoring system.
The Simplicity Score (SS) of a business text is the number of complete sentences in a sample of exactly 35 words. It is obvious that text simplicity increases with the number of complete sentences in the sample. The SS may vary on a five-point scale as follows: 0 (very hard), 1 (hard), 2 (standard), 3 (easy) and 4+ (very easy).
What’s the SS of the following paragraph from Gunning?
“But, while the Fog Index is handy for judging readability, it is not a formula for how to write. Don’t feel that you have written clearly just because your Fog Index is low. Anyone could put together a mumbo jumbo of short words in short sentences that would convey nothing at all to the reader.”
Let’s first draw an exact 35-word sample: “But, while the Fog Index is handy for judging readability, it is not a formula for how to write. Don’t feel that you have written clearly just because your Fog Index is low. Anyone could …”
The SS is 2 (standard).
All writers should do a bit of counting words and sentences and revise their writing for the sake of their readers. Before we send an article to the Press or a business proposal to a prospective customer, we should ask, “What’s the SS?”