Do Readability Scores work?

Flesch-Kincaid Grade LevelsSome seventy years on, the Flesch readability test is used by marketers, policy writers and bloggers; but do readability scores work?

Rudolph Flesch, a consultant with the Associated Press, devised a method for improving the readability of newspapers back in 1948. His Flesch Reading Ease measures the level of education needed to easily read a text. Today, the Search Engine Optimisation industry, blogging platforms and many publishers still swear by it.

The Flesch Reading Ease assigns a score from 1 to 100, to indicate how easily the average adult will understand it. The underlying mathematical formula seeks a ‘Goldilocks Zone’ of readability between 70 to 80. This is equivalent to the US eighth grade in school.

The US Navy produced the modified Flesch-Kincaid Grade formula in the 1970’s to make their technical manuals more readable. This again proposes an ‘ideal’ readability score of 8, or eighth grade level education for the average sailor.

Principles of Readability Tests

Both formulae are based on two principles:

  • Sentence length; the average number of words in a sentence in a text
  • Word length; which is the average number of syllables in a word in a text

Simple logic indicates that short sentences comprising short words are easier to read and understand.

The rules and weightings differ between the two formulae, however. Verb tense, passive and active voice and sentence construction all affect the scores.

In the Flesch-Kincaid Reading Ease, a higher score means the text is easier to read. A Flesch score of 60 to 70 is equivalent to eighth and ninth grade students. That is, understandable by 13 to 15-year-olds. Other scales of readability scores developed since Flesch use a lower score to indicate easier reading.

Readability formulas now permeate software text analysis tools. Some are tailored to specific industries, government, education or subject areas. The list is long and… a bit boring. Flesch-Kincaid remains in common use for general purpose analysis.

The Case For Readability Scores

Revising text according to readability scores can make a huge improvement. Documents such as product terms and conditions, technical manuals, classroom textbooks and presentations can all benefit. But so few do.

Meanwhile readability scores get applied to website copy, advertising copy, and… editing novels.

The Internet search engines have embedded readability scoring to promote websites to the largest possible audience. Consequently the Search Engine Optimisation industry does likewise. There are well-founded studies showing that a better readability score decreases bounce rates, increases site time and encourages content sharing. Allegedly, that increases sales and/or advertising revenue.

The Case Against

Slavishly working to readability scores can mean ‘writing down’ to the ‘average’ reader. General-purpose readability tools mechanically recommend dumbing-down any text put through them. Wave goodbye to style or expansive description including metaphor and simile. Everything becomes a grade-school paper.

What kind of novelist puts their work through Flesch-Kincaid? Dan Brown. Does this make Dan Brown a good writer?

Charles Dicken’s A Tale of Two Cities apparently “needs improvement on readability.” Dicken’s score of 50.4 in the Flesch test means “fairly difficult to read.” Downgraded for ‘too many words’, more than half of his sentences are in the passive voice. The Flesch-Kincaid formula promotes active voice at the top of its list. Does this make Dickens a bad writer?

Hemingway, on the other hand does well, as low as fifth grade. No wonder somebody built the Hemingway Readability app.

Meanwhile, political speeches consistently score in the eighth grade range, from Lincoln to Churchill. Rhetoric sits quite comfortably within the rules. Who knew?

Do Readability Scores work?

As always, the intended audience is the key. You don’t want a readability score determining every curriculum reading list.

You can also write easy text that scores well for readability without clarity or meaningful content. For that you need an editor. Don’t worry, AI will be along for that soon enough.

This post? This scores 49 in my WordPress plugin. The prosecution rests.

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