measure (14 categories)

Rates based on low numbers will be less reliable and should be interpreted with caution.

• The Crude birth rate is the number of live births per 1,000 population of all ages.
• The General Fertility Rate (GFR) is the number of live births per 1,000 female population aged 15 to 44, calculated using mid-year population estimates.
• The Total Fertility Rate (TFR) is the average number of live children that a group of women would bear if they experienced the age-specific fertility rates of the calendar year in question throughout their childbearing lifespan. The national TFRs have been calculated using mid-year population estimates by single year of age. The sub-national TFRs have been calculated using mid-year population estimates by 5 year age group.
• Age-specific fertility rates (ASFRs) are a measure of fertility specific to the age of the mother. They are calculated by dividing the number of live births to mothers of each age group by the number of females in the population of that age and then expressed per 1,000 women in the age group. The rates for women of all ages‚ under 18‚ under 20 and 45 and over have been calculated using mid-year population estimates for the female population aged 15 to 44‚ 15 to 17‚ 15 to 19 and 45 to 49 respectively.
• The mean (average) age of mother has been standardised to eliminate the impact of changes in the distribution of the population by age, enabling analysis of trends over time. The figure is therefore calculated using fertility rates per 1,000 female population by single year of age.

Our https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/livebirths/methodologies/userguidetobirthstatistics[User Guide to Birth Statistics] provides more detailed information about how rates are calculated.