I think you hit the nail squarely on the head, Mr. Waugh. It seems that the same gender biases that prevent entry into the boardroom then persist when there is representation, such that you have this enhanced level of scrutiny that wouldn't exist if it was a male CEO. This is one of the complexities of the business case.
When we're talking about traditional financial metrics, certainly there have been studies—as has been mentioned—that establish correlation between board diversity and profitability. It's important, though, to be mindful of the fact that correlation doesn't necessarily mean causation, such that if we put too much emphasis on the business case, we might then be putting unrealistic expectations on the shoulders of diverse directors, diverse CEOs, etc.