Book excerpt: Literature survey of statistical analysis and empirical studies dealing with relative wage differentials of unionized workers and nonunionized workers in the USA, 1967-1979 - reviews econometric models, evaluation technique and methodology employed for examining the impact of trade unions on wage structure; evaluates statistical methods, estimating the influence of race, sex, occupational status, regional disparity, size of enterprise, etc. On collective bargaining models. Bibliography, statistical tables.