Technical Notes: Demographic Indicators VARIABLE DEFINITIONS AND METHODOLOGY: Total Population refers to the de facto midyear population of a country. The United Nations Population Division compiles and evaluates census and survey results from all countries, adjusting data for the miscalculation of certain age and sex groups, misreporting of age and sex distributions, and changes in definitions, when necessary. These adjustments incorporate data from civil registrations, population surveys, earlier censuses, and population models based on information from socioeconomically similar countries. Population Growth Rate refers to the percentage growth in the midyear population of each country. Information collected through recent population censuses and surveys is used by the UN Population Division to calculate or estimate these parameters. Urban and Rural areas are defined by parameters that vary slightly from country to country. Many countries define an urban area by the total number of inhabitants in a population agglomeration. Typically the threshold for considering a region urban is between 1,000 and 10,000 inhabitants. Any person not inhabiting an area classified as urban is counted in the rural population. To see how each country defines an urban area, please refer to the following online PDF document maintained by the UN Population Division: http://www.un.org/esa/population/publications/wup1999/WUP99CH8.pdf. Population Density is calculated by WRI as the number of persons per square kilometer of land area. Population data are provided by the UN Population Division. Total land area is from the statistical database of the Food and Agriculture Organization of the United Nations (FAOSTAT). Percent of Population in Urban Areas refers to percentage of each country or region's total midyear population that lives in areas defined as urban. The definition of urban varies slightly from country to country. Many countries define an urban area by the number of inhabitants; typically the threshold for considering a region urban is between 1,000 and 10,000 inhabitants. Other countries specify several of their cities or provinces as urban, and the remaining population is defined as rural. To see how each country defines an urban area, please refer to the following online PDF document maintained by the UN Population Division: http://www.un.org/esa/population/publications/wup1999/WUP99CH8.pdf. Total Fertility Rate is an estimate of the number of children an average woman would have if age- specific fertility rate of the given year remained constant throughout her reproductive years. Information on the methodologies used to collect these data can be found in the technical notes for each variable in the EarthTrends searchable database, at http://www.earthtrends.org. FREQUENCY OF UPDATE BY DATA PROVIDERS: United Nations Population Division: Data sets contain estimates for every five years for all countries from 1950 to 2050. For 2001 to 2050, all data are forecasts based on assumptions enumerated below. The U.N. Population Division updates this information every two years, most recently on 28 February 2001. Food and Agriculture Organization of the United Nations: Data are available for most countries and regions from1961 to 2000. Data are updated annually by the Food and Agriculture Organization. DATA RELIABILITY AND CAUTIONARY NOTES: Population: United Nations demographic models are based on surveys and censuses with well- understood qualities, which make these data fairly reliable, although accuracy varies. Data are adjusted for overenumeration and underenumeration of certain age and sex groups (e.g., infants, female children, and young males), misreporting of age and sex distributions, and changes in definitions, when necessary. These adjustments incorporate data from civil registrations, population surveys, earlier censuses, and, when necessary, population models based on information from socioeconomically similar countries. After the figures for population size and age/sex composition have been adjusted, these data are scaled to 1990. Similar estimates are made for each 5-year period between 1950 and 1990. Historical data are used when deemed accurate, also with adjustments and scaling. However, accurate historical data do not exist for many developing countries. In such cases, the UN Population Division uses available information and demographic models to estimate the main demographic parameters. Land Area: According to Food and Agriculture Organization, the total area of the country includes the area under inland water bodies. Possible variations in the data may be due to updating and revisions of the country data and not necessarily to any change of area. SOURCES: Total Population, Population Density: Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat. 2002. World Population Prospects: The 2000 Revision. Dataset on CD-ROM. New York: United Nations. Population Change, Urban and Rural Populations: Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat. 1998. World Urbanization Prospects: The 1999 Revision: Urban and Rural Areas Dataset. New York: United Nations. Land Area, (population density calculations): Food and Agriculture Organization of the United Nations (FAO). 2002. FAOSTAT on-line statistical service. Rome: United Nations. Available on-line at http://apps.fao.org.