None Of Your Business
From the Hank Jr. song "If you mind your own business, you won't be minding mine."
It's amusing to me how many people are so nosy these days. I grew up in a different time, where we were taught to respect others privacy. But these days, it seems like I often am asked things that are quite simply none of the interviewer's business.
So, when I get a question like that, I don't get offended. I simply answer their questions with a question of my own. "how much money did you make last year?"
Of course, they get miffed and say "That's none of your business".