INEbase / >Population projections calculated from the 2001 Census / Methodology

Methodological summary on the calculation of population projects from the 2001 census.

The calculation of future population numbers by sex and age for the national, autonomous community and provincial total has been carried out by the components method which is the one used in practically all western countries who carry out this task.

The projection horizon was up to 2060 for the national total and fifteen years, in other words up to 2017 for the autonomous community and province total due to considering the low level of reliability of projections with this geographical breakdown beyond this period.

Populations have been calculated for each sex by simple ages for the national and autonomous community total and Ceuta and Melilla (respectively up to 100 and over and up to 85 and over) Melville by five year age groups for provinces (0-4 up to 85 and over).

The most important aspects are summarised below. The detailed methodology will be available during 2005.

The application of the component method meets the following schema: Starting from the resident population in a certain geographical area and data observed for each one of the basic geographical components, mortality, fertility and migration, the idea is to obtain population figures corresponding to subsequent dates under certain hypotheses on the future of these three events which are those which determine their growth and structure by ages.

Population numbers by sex and age, calculated from the 2001 population census have constituted the entry population on this occasion.

The hypothesis on the future evolution of the three demographical phenomena mentioned is mainly established from the figures observed on each one of them.

For the calculation of survivors and births vital statistics figures for 2002 and provisional figures for 2003 have been used.

Life expectancy at birth has been projected thirty years ahead, a period considered reasonable for extrapolation of the trends observed.

Future births have been deduced from fertility rates by projected ages.

With respect to foreign migration, to establish a hypothesis on its future behaviour, data observed for 2002 and 2003 have been used and estimated data for 2004. These arise from variations incorporated into the existing INE registry base.

For subsequent years, when establishing the hypothesis Spaniards and foreigners have been considered separately.

The considerable increase registered for immigrants in Spain over the last few years and the diversity of factors which have an influence on immigration implies a notable degree of uncertainty on the future of corresponding entry and exit movements. This has made it advisable to calculate projections under two different situations on its future.The corresponding results constitute situations that illustrate the consequences on growth and distribution of the population by ages of the different situations.

The hypotheses relating to mortality, fertility and migration are summarised in the attached tables.

Hypothesis on the evolution of demographic phenomena according to different situations.