Abstract:Labor unions provide workers representation and thus allow the collective action of the employees. This thesis discusses the effect of labor unions on the performance of firms and the responses that f...Labor unions provide workers representation and thus allow the collective action of the employees. This thesis discusses the effect of labor unions on the performance of firms and the responses that firms put in place in response to labor unions activity. The first chapter shows that the effect of labor unions on the performance of firms depends on the number and type of labor unions in the firms. Compared to a single labor union, the presence of several labor unions decreases the profitability of firms because the increase in wages is stronger than the increase in labor productivity. The second chapter focuses on the link between income smoothing and labor unions. Income smoothing reduces the union wage premium by reducing the risk perceived by labor unions on the sustainability of employment. Finally, the third chapter shows that gender pay gap, as a method for individualizing remuneration, limits the influence of labor unions within firms.Read More