It is hard to find out! The numbers in this April 2013 government study show just a tiny percentage decrease of senior women on Wall Street (30 to 28%). This study could not discern why and said so. So...we are left with questions. What is the culture we seek at firms? Who will be creating this culture if women are not inside the firms at a high level? How can firms gain diversity of thought, gender and backgrounds if their appeal to graduates and MBA's is slipping?
http://www.institutionalinvestor.com/Article/3244483/Search/Leaning-Out-Number-of-Women-in-Finance-Declines.html