Part of the problem with these kinds of surveys is it's hard to know if you're comparing apples to oranges. - Are they surveying base salary? Or total compensa

Part of the problem with these kinds of surveys is it's hard to know if you're comparing apples to oranges. - Are they surveying base salary? Or total compensation? Or perhaps just including bonuses? - Are the surveys voluntary? Life has taught me people lie about their income all the time.