I don't necessarily disagree with anything you're saying, I'm just not sure we actually need to go to the point of analysing our reading with stats!

The fact we can talk about a universal narrative that imposes assumed ethnicity, gender and sexual orientation on our reading is a clear sign that we need to become more diverse, if for no better reason than that it means authors are slipping into the lazy habit of not telling us some of the most basic information about characters!