One interesting fact to note, that WebAIM doesn't reflect at all, is the recent rise in usage of Chinese screen readers. ZDSR for Windows is still an insignific

One interesting fact to note, that WebAIM doesn't reflect at all, is the recent rise in usage of Chinese screen readers. ZDSR for Windows is still an insignificant and meaningless minority, but I'm not sure how long it's going to remain that way, considering it hasn't been available outside of China for very long. However, Commentary for Android is getting some significant usage, particularly in poorer countries where Android is the only thing most people can afford. It offers superrior experience and performance to Talkback, and isn't prohibitively expensive, so it's getting some popularity. I wouldn't worry about testing with those screen readers for now, as there still aren't that many people using them, but it's something worth looking out for in the future.