The comparison of projected fertility rates by age of the mother with those obtained from the Vital Statistics birth rate figures for the last years available (1995 to 1998) demonstrates that the forecasted average number of children per woman is greater than that observed. On the other hand, the age of maternity has resulted lower than that observed.

In order to carry out the present revision, the latest available figures on births have been taken into account (definitive ones for 1998 and provisional ones for 1999 and 2000).

In the 29 to 40 age interval, the short-term revised fertility rates, in other words, for the 1998-2005 period, have been projected taking the latest observed fertility rate trend into account. For the remaining ages, in other words, under 20 and over 40, the rates have been maintained constant and equal to those of 1997, due to the lack of weight they have on fertility and the oscillations that the corresponding series present.

To establish a reasonable hypothesis on the values that fertility rates will reach in the next fifteen years, in other words, between 2006 and 2020, the final descendance of successive female generations has been examined, analysing the information available on birth expectancy, marital status, the births by foreign mothers …

The evolution of marital status in Spain, which continues to be a conditioning factor of fertility, is characterised by its decrease in occurrence and its aging nature during the nineties. However, marriages have experienced an increase since 1998 that confirms the provisional figures for 2000. The situational indicator for first marriages registered a recovery in 1998, both for males and for females.

The births by immigrant mothers, according to the figures observed between 1996 and 1998, register a different fertility calendar than the rest of the population, with lower ages at maternity.

In order to obtain an average profile of fertility for the 2006-2020 period, the rates by age have been established with the following criteria: The rates for ages under 30 stop their decreasing evolution and remain constant in the 2005 figures. In the following ages, from 30 to 41, the fertility rates continue to increase, but at a much lower rate.

The fertility rates by age for 2020 remain constant until 2050.

To obtain births by Autonomous Community, a percentage distribution of the total has been applied to 1997, given that it presents notable long-term stability.

Births for each of the Provinces are obtained based on the births calculated by Autonomous Communities.