About the data
Definitions
Data sources

About the data

Knowing the size of a country’s population, its growth rate, and its age distribution is important for evaluating the welfare of its citizens, assessing the productive capacity of its economy, and estimating the quantity of goods and services that will be needed to meet future needs. Thus governments, businesses, and anyone interested in analyzing economic performance must have accurate population estimates.

Population estimates are usually based on national censuses, but the frequency and quality of these censuses vary by country. Most countries conduct a complete enumeration no more than once a decade. Precensus and postcensus estimates are interpolations or extrapolations based on demographic models. Errors and undercounting occur even in high-income countries; in developing countries such errors may be substantial because of limits on transportation, communication, and resources required to conduct a full census. Moreover, the international comparability of population indicators is limited by differences in the concepts, definitions, data collection procedures, and estimation methods used by national statistical agencies and other organizations that collect population data.

Of the 148 economies listed in the table, 129 conducted a census between 1987 and 1997. The currentness of a census, along with the availability of complementary data from surveys or registration systems, is one of many objective ways to judge the quality of demographic data. In some European countries registration systems offer complete information on population in the absence of a census. See Primary data documentation for the most recent census or survey year and for registration completeness.

Current population estimates for developing countries that lack recent census-based population data, and precensus and postcensus estimates for countries with census data, are provided by national statistical offices or by the United Nations Population Division. The estimation methods require fertility, mortality, and net migration data, which are often collected from sample surveys, some of which may be small or have limited coverage. These estimates are the product of demographic modeling and so are also susceptible to biases and errors due to shortcomings of the model, as well as the data.

The quality and reliability of official demographic data are also affected by public trust in the government, the government’s commitment to full and accurate enumeration, the confidentiality of and protection against misuse accorded to census data, and the independence of census agencies from undue political influence.

Population projections are made using the cohort component method. This method compiles separate projections of future fertility, mortality, and net migration levels by age and gender, then applies them to the 1995 base year age and gender structure. Future fertility, mortality, and net migration levels are determined from demographic models that use current levels and trends as inputs. Countries where fertility has been falling are assumed to have further declines at the rate of the previous 10 years until fertility reaches the replacement level of about two children. In countries where fertility has remained high, the transition to smaller families is assumed to occur at the average rate of decline of countries that are currently making this transition. Countries where fertility is below two children per woman are assumed to remain at this level for another decade, after which fertility rates will gradually return to replacement level. Similarly, mortality changes are modeled by assuming that the rate of change in the previous decade will continue in the near future. Future mortality in countries with high levels of HIV infection is adjusted to reflect the lagged impact of the disease on mortality.

Definitions

• Total population of an economy includes all residents regardless of legal status or citizenship—except for refugees not permanently settled in the country of asylum, who are generally considered part of the population of their country of origin. The indicators shown are midyear estimates for 1980 and 1996 and projections for 2010. • Average annual population growth rate is the exponential change for the period indicated. See Statistical methods for more information. • Age dependency ratio is the ratio of dependents—people younger than 15 and older than 65—to the working-age population—those age 15–64. • Population age 60 and above is the percentage of the total population that is 60 or older. • Women age 60 and above is the ratio of women to men in that age group.

Data sources

The World Bank’s population estimates are produced by the Human Development Network and the Development Data Group in consultation with the Bank’s operational staff. Important inputs to the World Bank’s demographic work come from the following sources: census reports and other statistical publications and electronic bulletins from country statistical offices; demographic and health surveys conducted by national sources; United Nations Department of Economic and Social Information and Policy Analysis, Statistics Division, Population and Vital Statistics Report (quarterly), and Population Division, World Population Prospects: The 1996 Edition; Eurostat, Demographic Statistics (various years); Council of Europe, Recent Demographic Developments in Europe and North America 1996; South Pacific Commission, Pacific Island Populations Data Sheet 1997; Centro Latinoamericano de Demografia, Boletin Demografico (various years); Economic and Social Commission for Western Asia, Demographic and Related Socio-Economic Data Sheets 1995; and U.S. Bureau of the Census, World Population Profile 1996. Projections are based on the methods discussed in Bos and others, World Population Projections 1994–95.

THE WORLD BANK METHODOLOGY:

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Size of the economy

Quality of life

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Key indicators for other economies

Population

Land use and deforestation

Growth of output

Credit, investment and expenditures

Integration with the global economy

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