Incomes don't follow a bell curve, so the choice of mean income is a red flag to me. Imagine you had 9 citizens making 100k and one billionaire, the mean is now 100,090k.

Relatedly, being in the bottom 10% doesn't necessarily mean the same thing in these different countries, in some of them that might not be below the poverty line so it's comparing apples and oranges.

If you worked in any larger company as well as looked at some of the people you studied with that somehow made the degree, and somehow got a well paying job even though they are idiots in that field, you should find plenty examples where it is not about trying or merit, but connections and favourable circumstance.

Daddy is in middle management? Well he'll get his idiot son in a nice paying position. Danny really did not understand what his uni class was about, but he could just learn everything by repetition, while Michael was working night jobs to afford food and could not take all the exams that semester. Maria is really smart and aced in school, but instead of going to Uni in a different city she took a local job because her parents cant take care of themselves anymore and their retirement money barely covers the rent and utilities...

I found it very eye opening when talking with two people from Uni once. The one was talking about his side job. The other one was getting everything payed by her parents, went to travel to very nice places and always prepared well for exams. She then said she also thought about getting a student job so she gets some relevant experience and a foot in the door. We had to explain to her that we dont work for that,but because we have to pay our bills and that it is taking quite a toll on finishing the studies in time.

Or could it be people already at the mean income look down on the poor and tend to choose someone from the mean income and above over someone below when the two people are otherwise equal?