I don't have access to the survey (boss won't share it), but the last one I saw had many variables, as they break it donw into regions, flight department size and so on.
In the "perfect" world we'd all be paid the same for the type equipment we fly. Alas, as you well know, salaries vary just by crossing the field!
Sorry I couldn't be of more help.
Regards,
2000Flyer