Maybe it's the result of individuals asynchronously but collaboratively acting to get the most for their class of people. Since there isn't a "council of women in technology" that meets bi-weekly to decide what each speaker should do for each conference, the women speakers act independently much of the time. To get the best for women they know they have to ask for stuff: fees, travel, tickets for other women. Men are not going to just give it to them. They try to do their level best there every time they get an invite. Every so often -- through casual conversation, meet-ups, online communities, articles in magazines, letters to the editor -- there is a chance to communicate about what worked and what didn't. There isn't an easy way for communication to happen about the net effect of speakers' actions for a particular conference when it's happening, or even afterward. There is a ratchet effect and in, addition, a general sense that "there is still more to be done" for women in technology. When the next conference rolls around, still more is attempted...