Women aged 16 years and over. By number of live births. Counties and Aran, areas and provinces

Historically, population censuses have included questions on the fertility of the female population. Since 1920, respondents have been asked about the number of live births and, as of 1930, the year of marriage. It should be remembered, moreover, that these kinds of questions are in line with the United Nations recommendations concerning the collection of census information for the study of female fertility.

The question about the number of offspring born varies in the collection of information of recent censuses. The 1981 census only included the question for women who were or had been married and left extra-marital births aside.

In the 1991 census, the question was addressed to women who had had live births, which hinders comparison of data with the previous census. The question on live births was addressed to all women who at some time of their life had had at least one live birth. Because of the wording of the question, the "non-answer" and childless mothers could not be distinguished. In fact, it should be assumed that all "non-answers" correspond to childless women in the census questionnaire.

This question was not included in the 2001 Population Census. In 2011, the question addressed the entire female population aged 16 and over and gathers information on the number of live offspring born, which enables studying retrospective fertility or cumulative fertility.

The ratio between the total number of children had by women of a certain age at the time of the census and the total number of women of the same age gives the mean number of offspring per woman for the age considered and is known as mean parity. Mean parity measures the cumulative fertility throughout life at the time of the census for the survivors of a female cohort defined according to the period of birth, but it does not provide information on the time of occurrence of births.

The mean number of offspring according to mother's age can be calculated for different groups of women of certain characteristics, such as civil status, level of education, the relationship with activity, etc. When assessing the results, it should be borne in mind that the characteristics of the mothers refer to the time of the census and not to the time of birth of the offspring.

The Population and Housing Census 2011 includes survey data. The results have been conveniently rounded up and are shown without decimals. Hence, some totals may not coincide with the sum of their disaggregation.

Unavailable information is represented using the symbol ":". When the value is lower than that of the minimum unit to be able to estimate the statistical operation or if it effects statistical confidentiality, the symbol used is "..".