Scope of the paper: systematic analysis of the causes of rigid union wage policies, 522. — Union objectives: income, 523; philosophy, 524. — Demand schedules for union labor: oligopoly, 525; product price rigidity, 527; partial unionization, 528; relative importance of labor cost, 529. — Misinterpretation of the demand schedules: imperfect knowledge, 530; socio-economic structure of unionism, 531; method of negotiating wage agreements, 533. — Arbitrators' decisions, 536. — Employers' attitudes and policies, 539.