Available information on births is used for the calculation of the main indicators of fertility intensity and calendar, at the national level, major socio-economic region (NUTS 1), region (NUTS 2) and province (NUTS 3) of residence.
For the study of the demographic determinants of fertility the diffused indicators are:
Fertility rates by mother's age x (or age-specific fertility rate) (fx): it is the ratio between the number of live births from women aged between x and x+1 years and the average number of resident women of the same age. The indicator is available for a single year from "15 years" to "49 years" and for the extreme age groups for "up to 15 years" and "50 years and over".
Total fertility rate (or average number of children per woman): it measures the fertility intensity. It is calculated as the sum of the age-specific fertility rates (fx), for ages ranging from 15 to 49 years.
Mean age of women at childbirth: it measures the fertility calendar. It is calculated as the sum of the products between the individual fertile ages (to which 0.5 is added) (from 15 to 49 years) and the corresponding age-specific fertility rates, compared to the total fertility rate.
Total fertility rate, mean age at childbirth, age-specific fertility rates by event year are disseminated for:
- Birth order, since 1952 for national level, major socio-economic regions, and regions, since 2003 for provinces;
- Citizenship of the mother, since 1999 for all the territorial levels.
Fertility data by order allow, in addition to the cross-sectional view by event year, a longitudinal interpretation by mother's cohort. The mother's birth cohort is obtained as the difference between the event year (year of the birth event) and the mother's age in completed years. Longitudinal data are disseminated annually for complete cohorts starting with the 1933 cohort for the national level, major socio-economic regions, and regions. At the provincial level, these data are not disseminated because for none of the cohorts considered is available the complete series of age-specific fertility rates useful for calculating the synthetic indicators (all ages 15-49).
With reference to the male population (without distinction by birth order and father's citizenship), the mean age at the birth of the child is also provided for fathers.
Nowadays, the main source for monitoring the births and fertility of the resident population is the administrative system National Register of the Resident Population (ANPR). In the past, data were collected through the compilation of Istat Form P4 operated by Register Offices of Italian municipalities (survey units), and then transmitted to Istat.
In order to calculate the fertility indicators, it is necessary to use data on the resident population from the “Intercensal population estimates by age and sex at January 1st” for years 2002-2019, and for more recent years, from the Census.
The variable “order of birth”, since it can no longer be collected directly, is estimated from the variable “number of minor members” reconstructed through the Municipal Registry Lists (LAC).
Average number of children per woman (total fertility rate): in a calendar year (event year), it is given by the sum of the specific fertility rates calculated by comparing, for each childbearing age, the number of live births to the average annual amount of the female population of that age. Referring to the generation, it measures the average number of children born at the end of childbearing life by 1,000 women belonging to a certain generation in the hypothesis of zero mortality.
Citizenship: the particular legal bond between an individual and his or her State, acquired by birth or naturalisation, whether by declaration, choice, marriage or other means according to national legislation.
Mean age at childbirth: average age at birth weighted with the specific fertility rates by age of the mother at birth (calculated by year of event or by generation).
Population register (Anagrafe): the continuous system of registration of the resident population. It is continuously updated through registrations for births from parents resident in the Municipality, cancellations due to death of residents and registrations/cancellations for change of residence from/to another Municipality or from/to abroad.
Resident population: constituted in each Municipality (and similarly for other territorial divisions) of people with habitual residence in the Municipality itself. Persons temporarily residing in another Municipality or abroad, for the exercise of seasonal occupations or for reasons of limited duration, do not cease to belong to the resident population.
Specific fertility rate by age: Ratio between the number of live births to women aged between x and x+1 years and the average number of resident women of these ages in a given year.
For the years from 1999 to 2001, the territorial detail refers to the territorial division existing (alternative: in force) in the considered years (103 provinces).
For the years from 2002 onward, the territorial detail refers to the territorial division used in the “Intercensal population estimates by age and sex at January 1st, 2002-2019” (107 provinces).
In 1963 the Molise region was established, which, separated from the “Abruzzi and Molise” region, became the 20th region of Italy (Constitutional Law No. 3 of Dec. 27, 1963). Therefore, data by year referable to the Molise region are available from 1964 and those by cohort from 1951 (complete cohorts). Cohort-specific rates from 1933 to 1950 (Fx by cohort) for the Molise region contain only some ages because they refer to incomplete cohorts. For the above reasons, for the Abruzzo Region, data by year before 1964 and data by cohort before 1951 refer to the “Abruzzi and Molise” region.
For the Autonomous Provinces of Trento and Bolzano, fertility indicators are calculated based on data available since 2003. Therefore, only data for Trentino-Alto Adige are disseminated for earlier years.