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birth-rate A measure designed to provide information on the comparative fertility of different populations, most commonly used in demographic analysis. A number of different calculations of varying sophistication may be used. The most well-known—the ‘crude birth-rate’—is simply the number of live births in a year per 1,000 population (using mid-year estimates). This measure takes no account of the age-structure of populations, which affects the numbers of women who are capable of giving birth in any year (the ‘population at risk’), and does not therefore yield particularly accurate comparisons. Multiplying the crude birth-rate by Area Comparability Factors produces rates adjusted for age and sex differences, allowing comparisons to be made between geographical areas, or across social groups within a society. The ‘general fertility rate’ is the birth-rate per thousand women of child-bearing age, calculated as the number of live births divided by the female population aged 15–44 years, times 1,000. These more sophisticated birth-rates take account of factors such as age-structure, but the more sophisticated the measure, the more data about the population are required for its calculation.