What is a readability score – and why should you be using it?

According to the National Literacy Trust, 5.2 million adults in the UK have a reading age of 11 or lower.

You wouldn’t expect an 11 year old to understand 50 pages of technical jargon – so why should you expect it from your customers? Many terms & conditions we analyse are far too complicated, which may be why only 16% of customers actually read them.

So how do you make sure your documents are easy to understand? Measuring the readability is a good place to start, but there can be a number of pitfalls to be aware of.

What are readability scores?

Put simply, a readability score puts an objective number to how easy to read a document is. This number is produced by using a ‘readability formula’.

A number of popular readability formulas exist. These include the Coleman-Liau Index, the Gunning Fog Score, and the SMOG Index. Perhaps the most famous is the Flesch-Kincaid Grade Level.

You can use these mathematical formulas manually to work out the ‘reading grade’, which is a type of readability score. You could also use an online tool to do the legwork for you.

We work out readability scores manually, to protect against inaccuracies. Our formula of choice is the Automated Readability Index (ARI), which is considered by many to be the most reliable. We’d recommend you using the same.

The Automated Readability Index

The Automated Readability Index (ARI) works off three figures.

The number of sentences, words, and letters is measured. With these numbers, the formula works out the words per sentence, and the length of the words used. Putting these together, it comes out with a reading grade.

The shorter the words and sentences, the lower the reading grade. So it rewards the use of short words and simple sentences.

Small is beautiful

Words per sentence has a profound effect on readability. The American Press Association states that an average words per sentence of 17 is considered ‘standard’. Anything over 30 words per sentence is ‘extremely difficult’ to understand. Therefore, keeping the words per sentence down is vital for readability.

On top of this, the use of short words is desirable, according to research from various groups. These include the Web Research Group and the Natural Language Processing Group. Furthermore, around 10% of the population has dyslexia, and shorter words significantly improves reader understanding amongst this demographic.

Our view on reading grades

Having analysed hundreds of financial documents, we’ve got a good idea of where the pitfalls are in terms of readability. But we also know where things can’t be changed.

Getting a document down to a reading age of 11 would serve the vast majority of the UK population. This reading age of 11 equates to a reading grade of 7.

We know that this can be very difficult considering the nature of the documents and the terms they need to include (although it is possible - and we've achieved it in some of the documents that we've rewritten for companies). Therefore, we advocate a reading grade of no more than 8 to qualify for our Clear & Simple mark. This would be suitable for a Year Nine pupil.

Most financial services terms & conditions still fall a long way short of even this level. In fact, many are only suitable for PHD students.

Lies and statistics

Readability grades are a useful guide as to how easy a document is to understand. But it's important to not get obsessed with them.

Once you've hit a low reading grade, it's important to check the content of your document and make sure it makes sense. We've seen a few documents that creep under our reading grade criteria, but still don't make a lot of sense to the average customer.

Nevertheless, if we reached a world where all terms & conditions had a reading age of 12 or 13, we'd be in a much better place than we are today.