https://phys.org/news/2018-06-boss-aware-incompetence.html

Comparing your performance to that of your colleagues, however, can become a detriment when your performance pales in comparison to that of your peers: "I have been working at this company far longer than Sara, but for some reason she received her second raise and I haven't even had one."

Would it be better for your boss to tell you why Sara got another raise and you are still waiting for your first? Or would it be better for your supervisor to keep the situation a secret?