As skeptics, atheists and humanists prepare to gather for their largest meeting in Las Vegas this weekend, attendance by women is expected to be down significantly.

Officials for The Amazing Meeting, or TAM, said Wednesday (July 11) that women would make up 31 percent of the 1,200 conference attendees, down from 40 percent the year before. A month before the conference, pre-registration was only 18 percent women, organizers said.