Between 1993 and 2005 Colombian municipalities experienced a polarization process, as municipalities' unemployment rates followed different evolutions that are relative to the National average. This process was been accompanied by the creation of unemployment clusters. This paper uses a spatial Durbin model to explore the influence of various factors in determining differences in regional unemployment rates and proposes a decomposition methodology to quantify how much of the variation in unemployment rate is explained by the variables included in the model and how much is explained by the variables omitted. According to our findings, differences in labor demand, immigration rates, and urbanization are factors behind the observed municipal unemployment disparities. This paper also explores whether different groups of regions will react differently to a labor market impulse.