Results of the 2016 GOV.UK assistive technology survey | Accessibility
The Government Digital Service have published the results of their assistive technology survey, which makes a nice companion piece to Heydon’s survey. It’s worth noting that the most common assistive technology isn’t screen readers; it’s screen magnifiers. See also this Guardian article on the prevalence of partial blindness:
Of all those registered blind or partially sighted, 93% retain some useful vision – often enough to read a book or watch a film. But this can lead to misunderstanding and confusion