Clearly, the individual worker is being immersed in an expanding association, over which he can have only decreasing control. […]  The powerful national union is replacing the individual, and we are faced with the prospect that there will soon be little personal bargaining left, and, by implication, small freedom of occupational choice. [(I don’t get it, but there personal bargaining is still dominant in the year 2001.)]  From the union’s point of view, control of the competitive job, whether locally, as in building, or nationally, as in steel or shipping, became an essential of survival.  It had to protect its members against the competing lower wages of the unorganized workers or run the risk of disintegration. [...] (p 117)

The worker’s organizations could not have survived, and the organized plants would have gone bankrupt if it had proved impossible to extend the union rules and their consequent costs to a whole industry. (p 117)

The national trade union is a response to monopoly, but not merely: “It hastens the growth of larger industrial units.”

Labor union monopoly: the case of the American Federation of Musicians.