screen reader user survey @ webaim.org, good all-round resource for
use ARIA you need a browser that both supports ARIA and is supported by a
screen reader that also support ARIA.
|- 75% of
respondents update to a new version of screen reader within 12 months.
|- Notice the very low percentage of IE 8 users.
|-So safe to assume that under 50% of screen reader users
can leverage ARIA functionality.