the discussion of diversity is very complicated and nuanced. I doubt any forum could due justice to any examination of the concept. And, to be fair, not my area of specialization so my experience is limited to just my hiring practices when I was in the role. On an aggregate level what you say makes total sense from a statistical pov. However, there are mitigating issues, not the least of which you need a minimum sample size of 30 to even be slightly significant but… And , for the record, when I was a hiring manager I took very seriously the federal civil rights act which “Prohibits discrimination in hiring, compensation, and terms, conditions, or priveleges of employment based on race, religion, color, sex, or national origin”. I purposely sought out people with perspectives different than mine. I didn’t want to hire a “yes man” …and, to your point, I had a very diverse team. Having never been on a board, I’m guessing they hire like minded individuals and, as a result, they may all resemble each other. Pure speculation, mind you.