The article looks at how wage differences are affected by how wages are set. They found that when wages are set centrally, the differences in pay between workers with different skills can either go up or down, depending on the types of workers involved. However, wage differences between workers in the same job but at different companies or industries always decrease with more centralized wage-setting. When there are both high- and low-paying jobs, a central union benefits from more workers being in the higher-paying jobs when the wage gap narrows.