A diversity audit can help you understand how diverse your current board is and spot the gaps.
Diversity audits can be revealing because not all difference is visible, for example class, sexuality or invisible disability. Some trustees may not want to disclose this information about themselves in a way that makes them identifiable, but they might be happy to do so anonymously, at the level of the whole board.
The results can help to focus attention and prompt action. Use a diversity audit as one tool in a wider discussion about the kinds of diversity that are important to your board, and how to build an inclusive culture.