INEbase / Intercensal estimates of population / Methodological summary

Population numbers by sex and age obtained in each census are used as a starting population to establish projections by the components method for the majority of Western countries

In turn, the populations calculated or projected may be compared a posteriori with the census populations on the corresponding reference date

The differences between the calculated populations and the observations produce breaks or ruptures in the population series and make it necessary to link or correct the projections established in concordance with the results of the successive censuses, as well as carrying out estimates of intercensal population

The differences which are normally found among the calculated and observed populations have their origin in the errors in the departure and arrival census populations or in the hypotheses carried out with respect to all or some of the projected components (mortality, fecundity, migration).

The measures for covering the censuses, made by means of evaluation surveys in the majority of countries, do not facilitate correcting resulting populations (the publications may be consulted) Evaluation of the population forecasts elaborated from 1981 Population Census results. INE 1990 and population projections for Spain calculated from the 1991 population census. Evaluation and revision. INE 2001

Therefore, given the impossibility for distinguishing the part of the error which comes from the differences in the subregister or the overnumeration in two successive censuses, of the part due to the incorrect estimate of the components, the hypothesis is made that the final error obtained is distributed linearly during the intercensal period.

This procedure has been applied generically to obtain populations by sex and age, coherent with the results in the 1970, 1981, 1991 and 2001 population census.

The specific demographic information and characteristics from the three periods included between the aforementioned censuses as well as the intermediate results obtained in the application of the method are set out in the corresponding publications which - for the periods 1970-1981 and 1981-1991 are available in printed format and for the period 1991-2001 are in elaboration phase

The calculation of intercensus population estimates carried out for the period 1970-1980 is covered in the publication Evolution of the population in Spain between the 1970 and 1981 censuses. INE 1999, which is made up of a printed part and another on magnetic support. The methodology used is described in detail in the printed monography which also contains a summary and observations on the results obtained.

The information and results corresponding to the period 1981-1990 are covered in the publication Evolution of the population of Spain between the 1981 and 1991 censuses. INE 1996, which is also made up of a printed part and another on magnetic support