"More sophisticated pieces of analysis carried out by academics have shown very small positive correlations between female board members and financial success. But this is an average – in some companies the relationship was neutral and in some it was negative. And proving causation is far harder."

[COMMENTARY] Ethical investors are convinced that having women on boards improve corporate financial performance. Studies support that thesis. However, this article cites some research contradicting that finding. So, who’s right? As in most social science research, results can differ greatly between studies.
100 Women: Do women on boards increase company profits? October 2, 2017, BBC News, UK.