Race and Age Impact Tech Salaries

Hired study concludes Asian tech workers leapt ahead while their black counterparts slipped further behind; U.S. engineering salaries plateau at age 40

How do the study account for years of experience and academic qualifications?
Only rank and files or include managers, directors and VPs+
Tech professionals are not SWEs only right? The starting salaries at FB, GOOG, NFLX are higher than the average salaries and most SWEs there plateau at $300k-$400k.
How do they account for position like CEO GOOG, CEO MSFT, CEO ADBE, CEO MU, CEO INTC, … ?