Keep in mind they mean it when they say optional ("You may address any subject you wish, such as being a first generation college student, or being a part of a minority group (whether because of your sexual orientation, religion, economic status, gender identity, ethnicity), or being the child of undocumented immigrants or being undocumented yourself, etc. Please note that this question is optional and that you will not be penalized should you choose not to answer it.). You don't need to come up with a general diversity statement. If you don't have something huge/obvious that is going to matter a lot to their understanding of your background, I say skip the question. I skipped it myself!