Wages maxed out at $25

I'm on my third play through. The first two times, I was able to raise wages to whatever I wanted.

On this play through though, I can't raise wages past $25. There's a red line half way down the slider showing the hard limit. This is going to be a problem because my high school education wage is approaching $20, and I don't want to discourage people from going to college.

Why can't I raise wages past $25, and how can I fix it?