Found out your colleague makes more than you? Here's what to do about it
https://money.cnn.com/2018/09/05/pf/coworker-makes-more-salary/index.html
This becomes an issue in skills and qualifications-based society.
In Japan, no one officially complains about wage gap between workers in the same positions, because they take it for granted that payrise is based on age or how long an employee is in a company.
So, they will never take it seriously as long as there is an age gap between workers.
However, as private conversation with colleagues, we often hear complaints like "Why does that elderly man is payed more than I, even though he does nothing?"