Choosing a suitable interval for selling company stocks is a standard device for professional bullshitters like Credit Suisse (professional bullshitters because they have to make up fairy tales to sell stock when nobody really can predict anything). If they had taken another interval, the results would have been different. I think this was even obvious from the charts they included in the study (it's been a while that I read it - anyway, I encourage everyone to do the same).
If the theory is correct and women take less risks, then presumably the climate between 2005 and 2011 favored less risk taking (bear market?). At other times, more risk taking might have been more beneficial.
It's actually well known that it's almost always possible to pick an interval on which any given stock shows a positive performance.
And there are of course the other possible explanations, for example that successful companies might have an easier time attracting women because they can afford special perks to lure them in.
It's amazing how often this Credit Suisse "study" has been cited by now. Many people just take it at face value because it suits their ideology.
I wish people who believe it would just invest in female led companies or start an index fund of such companies. Let the market sort it out.
(I have nothing against female leaders, just against ideological fairy tales).