ASFR

ASFR, short for age-specific fertility rate, is a demographic measure that assesses the fertility level of women in a specific age range. It is typically calculated for five-year age groups (for example 15–19, 20–24, 25–29, and so on) and expresses the number of live births per 1,000 women in that age group within a given year.

Calculation and interpretation: For a given age group x–x+4, ASFR_x = (B_x / N_x) × 1,000, where B_x is the number of births to women in that age range during the year and N_x is the mid-year population of women in that age range. The resulting figure shows how fertility is distributed across ages, highlighting whether childbearing is concentrated among younger or older women or spread more evenly.

Relation to other measures: ASFRs are the building blocks of the total fertility rate (TFR). The TFR approximates the average number of children a woman would bear over her reproductive life if she experienced the current ASFRs; it is computed by summing ASFRs across all age groups and multiplying by the width of the age interval (typically 5 years). When ASFRs are expressed per 1,000 women, an adjustment by dividing by 1,000 is made to obtain births per woman.

Data sources and limitations: ASFRs rely on accurate birth counts and reliable age reporting, with data often drawn from civil registration, censuses, or demographic surveys. Limitations include underregistration of births, misreporting of ages, and sampling error in smaller age groups.

Uses: Researchers use ASFRs to analyze fertility patterns, compare regions or populations, monitor fertility transitions, project births, and assess the potential impact of policies or socio-economic factors on age-specific childbearing behavior.