And the survey says: diversity (gender, region of residence, professional functional area (eg accounting), culture and ethnicity) is among one of the top four areas needing improvement for nonprofit boards.
This data comes from a survey of 350 execs and senior managers who participated in executive education programs at the University of Notre Dame's Mendoza College of Business a group I would judge may be a bit more enlightened that the average nonprofit exec (suggesting that they are pursuing academinc education and may well have had a conversation on this matter) but let's suggest that this 350 are an indicator of the broader nonprofit pool of execs.
In that case, for those valuing diversity on board, the best answer: consider adopting a multilevel structure that creates opportunities to involve more individuals in varying roles. Next, recruit using other means that your board members -- afterall, the folks they know have characteristics that are likely just like them. Another problem for achieving divversity goals: boards without or not enforcing term limits. In the survey, 25% of the boards don't enforce their term limits.
And, still on the matter of diversifying, creating an outer "friends" group as a feeder body comprised of donors, volunteers and or serving on committees or task forces can help diversify in the long run.
Nonprofit board diversity is not that difficult but it requires intentionality and commitment and a real appreciation of the many benefits to the organization to pursue.