Another important facet in the diversity conversation:

Economic class.

From the Guardian:

Publishing is in dire need of readers and yet, because of ingrained perceptions, millions of readers are unable to read about their experiences because those who commission and market new writing feel uncomfortable with something they know so little about.

There is a belief in publishing that books set in the north with working-class characters are too "small" and don't fit the middle-class demographic who will be interested enough to buy such books.

I don't agree with every single thing he has to say, but I would like to see more depictions of characters and families across a broader economic spectrum. They've definitely been on the rise—I've been seeing more and more stories where characters have to deal with budgetary concerns—but I still want MORE.