During my tenure with the company, I observed wage discrepancies for the same jobs. Management also stated that we were not allowed to discuss raises or salaries with other employees, which is a violation of the National Labor Relations Board. All employees are legally permitted to discuss pay while not at work or on the clock. It would be prudent for all employees to be open about wages to ensure just compensation. If HR or Department heads make any threats about disclosing wages/raises to other employees, it should be reported. Also, the company is prohibited from retaliating should you discuss wages amongst your peers.
https://www.nlrb.gov/about-nlrb/rights-we-protect/your-rights/your-rights-to-discuss-wages