I actually just went through this. I was promoted into management and new managers being hired externally are coming in at 6k more annually. I asked... for a raise. Didn't get matched but I got SOMETHING  more

Try to find out some new skills that can make you more marketable and competitive

By being committed, hardworking and intelligent enough at your work sections with integrity

Take it as learning point so that your next opportunity you not take it as an interview but a discussion were you market yourself and freely express... how much you are wealthy. Don't be skeptical when you are asked your salary expectation.
my expression here is that new hires invested in marketing and bargaining skills which probably you might be lucking.
it has nothing to do with qualification. more

The question is okay but if feel it is not guiding much. Kindly furnish if the new hires have same qualifications with you.

Invest in yourself and improve on your skills and start applying else where. And when the right pay and company comes along, you move. Always look out... for you
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I would start interviewing elsewhere, see what they are offering you, and negotiate with my current employer.

By being polite and calm

Get a new job somewhere else, you stayed at this job 3 years too long already.