I understand what you mean — but:
For most kinds of comparison the figures should necessarily be the gross salary figures, because due to the very different income tax systems, both for a cross-state-border comparison, as well as and even more for an international comparison, the net salary figures weren't actually useful.
Let's say:
State XYZ funds 25% or even less of its population's education — these might be the US states with a very low or no state income tax;
State ABC funds 75% of its population's education — almost certainly they must have a state income tax there.
Of course [especially, if net figures are used], these taxation/health and social insurance/education costs and some more peculiarities of the States or nations in question should be pointed out precisely.
But most charts don't (cannot) do that, and that's a dilemma of these comparisons.
When comparing all 50 states it would be good to know if all of this median income was taxable income (federal income tax).
If a person makes $30,000. does he make that in taxable wages?
Back in 1999 I made $60,000. and my employer paid all of my insurance, including co pays and deductibles, I had no health care costs.
Today if one makes 60,000 and we adjust for inflation he makes 41,000 compared to my earnings of 1999, but then most workers are clobbered with a premium of around $1800. per single person and sometimes $5000.00 or more per family, along with a deductible
that can run in to thousands (I know of several who have a $5000.00 deductible per family).
Suddenly this $60,000 reduces for inflation to $41,000. then reduced for health care premiums by a few thousand more with a looming deductible and co pays is not much money, yet we see medium incomes on that map from around 19000. to a high of 40,000.
My point in all of my posts in this thread is to show how the American workers wages have been incrementally, systematically and intentionally brought down and how the money that they once made has been funneled to the 1%.
If this would have happened over a short period of one year there would have been riots.
The worker today is like the battered wife, she gets used to the abuse, puts up with the injuries and insults and one day her husband come home to find her waiting with his shot gun. There is a breaking point.