The latest study I've seen in this highly contested field says that diversity doesn't improve corporate performance or profitability:
This article examines the debate within corporate governance about the appointment of female non‐executive directors (NEDs). The first part tracks the diversity story that corporate governance tells about itself from the Cadbury Report (1992) to the Davies Report (2011). The second sets out the evidence used to support the argument that female appointments enhance profits and corporate profile. The third part presents the authors' empirical analysis of FTSE 100 companies and female nonexecutive board membership, and concludes that there is little evidence that companies with female board membership display different characteristics from those without. Industry sector emerges as a significant factor in female appointments. The idea that women should be appointed to boards to increase corporate profitability and profile is not strongly supported by this analysis. A social justice argument based upon the right of woman to equal economic participation opportunities provides a much superior articulation of the need for boardroom diversity.
The trouble with those "social justice" arguments, of course, is that they bump up against the justice-based arguments against preferences and quotas.
