In 2011 the 15th Population and Housing Census was based largely on the use of the Municipal Population Registers. Census results showed that 2,383,071 residents were not counted. For the first time, this number of uncounted residents has been available at the individual level.

As required by the Italian law, after the Census the Italian Municipalities must do the revision of population registers, under the supervision of the Italian National Institute of Statistics (ISTAT).

The results have been reported in the informative system for the documentation of Municipal Population Registers Revision, called SIREA (“SIstema di REvisione delle Anagrafi”), realised by ISTAT.

The aim of this study is to analyse the risk of not being surveyed by the Census. In order to point out which factors contribute the most to the exclusion or inclusion in the Census survey, a logistic model was applied to estimate the probability to have the usual residence in the municipality versus to be deregistered.