The Residential Variation Statistics are compiled using the register entries produced in the INE database, as is described in the General methodology. However, by calculating the net migratory balance as the difference between external Registrations and Cancellations due to residential variation, the resulting balance does not coincide with the balance that would be obtained as the difference between the population figures from the register and the natural increase produced during the year. These discrepancies are caused by the following methodological features:
1. Variations included during the statement period. Durante el período de alegaciones del procedimiento de obtención de las cifras oficiales de población se "recuperan" variaciones (altas y bajas) que no habían entrado en la base del INE en el momento del cierre de la EVR y que, por tanto no se tienen en cuenta en la estadística pero sí en las cifras de población a 1 de enero.
2. Registration by Omission (RBO). The Registration by Omission of Spaniards, as opposed to that of foreign nationals, is not included in the RVS, because it is not considered to be strictly migratory movement, given that there always remains the possibility of contrast with existing registers (previous Dwelling Register or Register of Spaniards Resident Abroad, if they did not reside in Spain), in the event that the citizen claims not to have been previously registered, and a previous registration is not located in the INE database. However, it is reflected in the population figure.
3. Cancellations for Undue Inscription (CUI). The CUI of Spaniards, as with the RBO, are not considered to be migrations, but rather adjustments in the register, and they are not included in the RVS, but do have a repercussion on the figures at 1 January.
4. Variations from previous periods. In the monthly variation files, the INE not only receives movements corresponding to the previous month, but also to previous months and even years. These variations are included in the current year's population figure, but not in the RVS, which only includes residential variations relating to the reference year, and which are received up until March of the following year.
5. Natural increase. The natural increase (Births-Deaths) from the Civil Register does not coincide with the natural increase taken from register entries, which is obtained as the difference between registrations due to birth and cancellations due to death.
6.- Differences due to entries that are neither renewed nor cancelled after the expiration date of the NCFNWPRP (Non-Community Foreign Nationals Without a Permanent Residence Permit). For the data from the year t, the following cases are highlighted: