Knowing Everyone’s Salaries Can Light a Fire Under Workers

TL;DR: employers want to say that sharing the salaries is counter-productive (because employers want the freedom to set unfair salaries).

Employees are generally happier and hence more motivated when the salaries are fair.

Employees are generally less happy and hence less motivated when the salaries are unfair.

Feels like it shouldn't require advanced research "from Indiana University, Harvard Business School and the University of California" to realize that :).