Statistics on a11y
Statistics on disabilities, as well as on accessibility issues, are valuable for shaping advocacy messages.
Accessibility issues on the web
Various organisations collect representative data about the state of accessiblity on the web.
Automated analysis of the million most popular websites in the world, using the WAVE tool.
https://www.levelaccess.com/2020-state-of-digital-accessibility-report/
Disabilities
General
Who Can Use
"Who Can Use" by Corey Ginnivan differs from other colour contrast tools in that it not only highlights the contrast of a chosen colour combination, but also presents instant statistics what share of users might be negatively impacted by it and simulates how they would see it.
Handy, not just for design verification, but first and foremost as an educational resource.