A population of a country, or other defined territory, grows as people are born or migrate into it, and it lessens as people die or migrate out. The birthrate, which is most often called the crude birthrate because it is a simple measure, is the rate at which the population grows due to births over a reference period. Conventionally, it is the number of infants born alive in a calendar year per 1,000 population at midyear. The rate is accurately calculated using live birth counts from a universal system of registration of births, deaths, and marriages, and population counts from a census. Otherwise, it may be satisfactorily estimated by application of specialized demographic techniques. If the death rate and migration rates are known, together with the birthrate, the population growth rate can be calculated accurately.
The birthrate alone may still be used as a proxy for population growth, because it is usually the largest component of population growth. As there exist better, noncrude measures of births— known as fertility rates—that take account of the age distribution, relative group size, and mortality of potential mothers, the principal use of the birthrate is as a summary indicator of population growth. Typically, a birthrate of 10 to 20 per 1,000 is low, and a rate of 40 to 50 per 1,000 is high. In the absence of other information, a high birthrate is assumed to be a general indication of health impairments and low life expectancy, low living
The world birthrate is estimated to have been around 37 per 1,000 in the early 1950s, and it is estimated at 21 per 1,000 in 2000. Since the 1950s, the birthrate for all Europe is estimated to have fallen from 21 to 10 per 1,000 (in the United Kingdom, the birth rate fell from 16 to 11 per 1,000); in the United States from 24 to 14, Canada 28 to 11, Australia 23 to 13, and New Zealand 26 to 15 per 1,000; in Latin America to have dropped from 42 to 22 per 1,000; in Asia to have halved from 43 to 21 per 1,000 (in the People's Republic of China alone, the birth rate fell from 44 to 16 per 1,000); and in sub-Saharan Africa to have declined from 48 to 41 per 1,000. A well-conceived public health strategy is likely to include provision of a range of contraceptive and other family planning services as part of broadbased health interventions designed to attain sustainable economic as well as social improvements.
Shryock, H. S., Siegel, J. S. et al. (1971). The Methods and Materials of Demography. Washington, DC: U.S. Government Printing Office for the U.S. Bureau of the Census.
United Nations (1999). World Population Prospects: The 1998 Revision. New York: United Nations Department of Economic and Social Affairs, Population Division.