Does your data include a lot of Canadians? One of my earliest posts showed you how to create an indicator variable to distinguish rural dwellers from people who live in an urban area or small town. See Rural vs. urban postal codes. I have sometimes found a significant difference in giving levels between the two groups.
During the month of August I will be posting new material slightly less often, but calling attention to previously-posted material that had low readership because the blog was still very new.