What they are, why they matter, and how to use them
Readability assessments (or indexes) aren’t getting much love because the formulas don’t account for aspects of design and structure that make text easier to read (like subheadings, lists, and illustrations). The critics point out that nonsense text can pass a readability assessment with flying colours. Well, The Jabberwocky is well punctuated, but that doesn’t mean we should throw out grammar. Spellcheck isn’t perfect, it’s still an indispensable tool.
They have their uses, readability indexes do, primarily as an objective, measurable assessment that editors can use to support their argument for simplifying the language in a piece they are working on. Some even take vocabulary into consideration.
In my Technically Speaking column in the Oct-Nov 2016 Copyediting Newsletter (available by subscription), I explain the various indexes and outline their pros and cons. Plus, I direct you to online tools that will perform the assessments for free.
Photo Walt Stoneburner, used under CC BY-2.0 license.