Help! Assessing the Gendered Conference Campaign

There seems to be anecdotal evidence that the gendered conference campaign (see pages above) has led to more women being invited as keynote speakers at conferences. How might one get a quantitative assessment of its effectiveness?

That might look easy, but it looks hard to me. Presumably we should start by counting and comparing. But that supposes determining what to count, and that’s less clear. Of course, it would be conferences and invited speakers, but how might one select groups of conferences to be enlighteningly compared?

It would be great to get some suggestions!