How to get socioeconomic information without asking income?

I am conducting market research about banking habits and I will be using mostly business owners and financial professionals as my subjects. The format will be personal interviews and I would like to ask about their personal financial habits as well as their business banking needs. I have a feeling that these financial professionals will not be too open to sharing their personal information in a "B2B" interview. How can I get information about their socioeconomic status (generally) without directly asking the dreaded income question?How to get socioeconomic information without asking income?Ask them approximately how much they spend on their credit cards. That will give you an idea of how wealthy they are. Someone's expenditure is a less personal question than what their income is, but you can infer their income from the answer.