Well I just looked at the first paper, and now look at the credit suisse paper I linked in another comment ( https://www.credit-suisse.com/newsletter/doc/gender

Well I just looked at the first paper, and now look at the credit suisse paper I linked in another comment ( https://www.credit-suisse.com/newsletter/doc/gender_diversity.pdf https://www.credit-suisse.com/newsletter/doc/gender_diversit... ) which has charts for 2005 to 2011. There was a "crash" in mid 2007 that somehow reversed the trends for companies with or without women on the board. Before that, zero-woman companies were outperforming the woman-companies. Now it seems rather curious to me that they choose 2004-2008 for their comparison (in the first paper you linked to). So strangely, they catch exactly that crash point in their interval. It's always the same shenanigans...