voiceover speech in words per minute?

[Karen Lewellen]

Hi folks,
There is a research from the WAI interest group,
www.w3c.org/wai
Who is doing a presentation on the ability of users to process  using 
screen readers at often very fast words per minute.
He desires including all platforms, with Voiceover rates only set in 
percentages.
Anyone have  a good source for how those percentages translate into wpm in 
voiceover on the mac or in Ios?
Thanks,
Karen