Some questions I did not see answered in the article:

1 Does the average "typical worker pay" include the global workforce?
I imagine all of these companies in the study operate in developing countries and would therefore lower the average worker comp.

2 What is the domestic company payroll budget now vs then? How many employees are on payroll?
The feminist movement has greatly increased the workforce (for better or worse). If company output hasn't matched this offset, overall pay has to go down. This is actually a major driver of household inequality. If 2 jobs now are economically equivalent to 1 to 1.5 in 1978, how can a single-earner or single parent household even dream of keeping up?