Comparison between census data and other sources has been, in the last years, one of the preferred subjects among statistical users and opinion leaders. In this way, this paper compares last census data with data from electoral register, identifying responsible factors for the existing differences; key factors responsible for these differences are deaths not erased and persons with usual residence abroad but also enrolled in the Electoral register as resident in Portugal.

Keywords: population census, census 2001, electoral register, data comparison, administrative registers