Because it's a generalized demographic poll, they consider it to be an averaged sort of thing. It gives advertisers an idea of the income spread of listeners of the show.
Advertisers who are looking to buy local spots with stations that run our show will interpret the poll one way...
Advertisers who are looking to buy national advertising will interpret the poll another way...
Since we are primarily a national show, and sell to national advertisers, a localized poll isn't necessary, and the income results here are already translated, no matter where you are from, to a national income scale.