It somtimes depends on where you live and.... but mostly your name and reputation.
Pretty stupid project. You can't measure somthing like this unless it is mandated by the gov't or you work in a socialist society.
I know artists and actors who make millions a year, and I know others who make barely break poverty.
Bottom line, there is NO system to how much you make.
"If one advances confidently in the direction of
his dreams, and endeavors to live the life he
has imagined, he will meet with a success
unexpected in common hours."
- H.D. Thoreau