The term ‘Diversity’ is often thought of as a cultural thing just as ‘Accessibility’ is thought of as disability thing. The concept of universal design doesn’t separate these and doesn’t separate them from what’s considered mainstream. That’s the meaning of inclusion and inclusiveness. But let’s not get hung up on the words.
Diversity covers gender, ethnicity, age, size and shape, income, education, language, culture and customs. There is no Mr or Ms Average – it’s a mythical concept. Dan Jenkins writes about diversity as inclusion for the Design Council and makes this observation;
“Often, it’s a perceived efficiency-thoroughness trade off – a variant of the 80:20 rule, that crudely suggests that you can get it right for 80% of the people for 20% of the effort, while it takes a further 80% of the effort to get it right for the remaining 20%. However, much of the time it is simply that the designers haven’t thought enough about the diversity of the people who wish to interact with the product that they are designing, often because it’s not in the culture of the company.”
It’s not just disability
Similarly to Kat Holmes, Jenkins says to think of capability on three levels:
1. Permanent (e.g. having one arm)
2. Temporary (e.g. an arm injury)
3. Situational (e.g. holding a small child)
“The market for people with one arm is relatively small, however, a product that can be used by people carrying a small child (or using one of their arms 
for another task) is much larger. As such, designing for the smaller market of permanent exclusions is often a very effective way of developing products that make the lives of a much wider group of customers more flexible, efficient and enjoyable.”
Jenkins reminds us that all our capabilities will be challenged eventually, either permanently or temporarily. That’s why designers need to think of the one arm analogy in their design thinking. Excellent easy read article from the Design Council. Infographics are taken from the article.
Much of Jenkins’ content is similar to Kat Holmes material and the Microsoft Inclusive Design Toolkit. There are three articles on this website that feature Kat Holmes:
What does inclusion actually mean?
What is the meaning of inclusion in inclusive technology?
Also Kat Holmes book, Mismatch: How Inclusion Shapes Design,