As indicated previously, the Blinder-Oaxaca decomposition does not identify whether the unexplained part is discrimination by employers or unobserved heterogeneity in productivity. Three combinations are taken in the matching: set I takes age and year, set II adds education measured by three dummy variables, and set III adds the head of household dummy variable. As Marquez Garcia, Nopo and Saiardi (2009) highlight, the greater the number of characteristics used in the matching, the smaller the chances of finding exact matches.