Ah, but then one of the unions could free-ride on the sacrifices of the others, and the whole system would collapse bit by bit! No, if you have multiple unions,

Ah, but then one of the unions could free-ride on the sacrifices of the others, and the whole system would collapse bit by bit! No, if you have multiple unions, then obviously they need to form a union-of-unions to allow the unions to collectively bargain.