The aim of this thesis is to examine the relationship between union’s indicators namely union density rate and collective bargaining coverage rate, and the unemployment rate. I have conducted an empirical analysis on 34 OECD countries grouped into three groups based on their bargaining systems. The results indicate that there is no linear relationship between union density and collective bargaining coverage, and the unemployment rate in countries which have centralized co-ordinated, organized decentralized but co-ordinated bargaining systems and that those systems do not have influence on the way unions affect unemployment rate. However, the predominatly centralized but weakly co-ordinated system indicates to have a positive effect on the way unions affect unemployment rate and union density /collective bargaining coverage are positively related with the unemployment rate in this group. I try to argue for possible reasons for these findings.