Hi everyone,
I too am uncomfortable with the "under 20%" message. I would say "around 10% according to the most recent editor survey".
In 2011, the WMF set a target of having 25 percent of its contributors identifying as female by 2015. The "under 20%" message may give the impression that we are almost there.
Re:
(personally, I prefer the wording "less than one in five" which is mathematically identical but a bit better at avoiding to evoke the kind of false sense of precision that has developed about this topic at times).
The highest reasonable estimate we have is 16.1% (2008 survey data corrected for sampling bias by Hill and Shaw). That is less than one in six.
Cheers, Su-Laine Brodsky (née Su-Laine Yeo)