Many of them have an, "I prefer not to answer," option at the bottom of the list.
I have never been concerned about stating household income because it is part of my demographics. My household income would make me eligible to purchase many 'upscale' things I would never waste my money on, but on the comfort level of things, I would rather do a shop at Coach than at a check cashing place. And as for someone paying Social Security for a transcript of my employment earnings, that is nonsense because Social Security likely would not be reporting out my monthly SS check, nor would they have information for capital gains, interest and dividends, all of which contribute substantially to our household income.