The Effects of Unions on Employment and Productivity: An Unresolved Contradiction
指出，工会显著提高生产率的证据与工会对就业影响较小的证据相矛盾。如果工会受企业需求函数约束，且需求函数中使用的是效率劳动单位，那么解决这一矛盾的关键在于工会提高资本生产率（而非劳动生产率），且劳动与资本替代性极低。但替代性参数估计接近1，因此要么工会未显著提高生产率，要么工会显著减少了就业。
The evidence that unions substantially increase productivity is contradicted by the evidence that the effect of unions on employment is small. It is shown in this paper that if the union is constrained by the firm's demand function, and it is the efficiency units of labor that are in the demand function, then essentially the only way to resolve this contradiction is for unions to raise the productivity of capital (and not of labor) under conditions where the substitutability between labor and capital is very limited. But estimates of the substitutability parameter are near unity, so that one of these effects must be wrong: either unions do not substantially increase productivity or they substantially reduce employment.