Unions in effect are powerful only when they can change their income without affecting their productivity. Voluntary unions can achieve productivity gains by be

Unions in effect are powerful only when they can change their income without affecting their productivity. Voluntary unions can achieve productivity gains by being another form of organization, that I grant and thats why I see value in freedom of association. But that is not the union people imagine or want when bernie Sanders calls for them. They imagine the power of changing wages at will.