Why Do Unions Oppose Merit Pay?

Bryan Caplan

Gary Becker off-handedly remarks:

Not surprisingly, teachers unions fight hardest against reforms that change the way teachers are paid, especially when they introduce incentives for teachers to perform more effectively.

I don’t doubt that unions tend to oppose merit pay, but the reasons are unclear. Profit-maximizing monopolists still suffer financially if they cut quality; the same should hold for unionized workers. Why not simply jack average wages 15% above the competitive level, and leave relative wages unchanged?

Tyler Cowen has more.