This survey outlines the main trends and determinants of unionization and collective bargaining across a wide range of countries and regions. It shows that union membership and density as well as bargaining coverage have fallen in most countries and that collective bargaining has become more decentralized over the last decades. However, there is a considerable amount of variation across countries and between different indicators of unionization and collective bargaining. Unionization is found to be related to a large number of structural, cyclical, institutional, and sociodemographic variables. Although changes in the sectoral structure of the economy and the composition of the workforce have played a role, their contribution to union decline seems to be smaller than widely believed. The effect of globalization on unionization and collective bargaining as well as the role of changing attitudes of employees towards unions have not been fully clarified, but the rise of the informal sector in various parts of the world