World Population clock statistics: sources and methodology
The world population counter displayed on Worldometers is based on analysis of data from two major sources: the United Nations and the U.S. Census Bureau.
1.The United Nations Population Division of the Department of Economic and Social Affairs every two years calculates, updates, and publishes estimates of total population in its World Population Prospects series. These population estimates and projections provide the standard and consistent set of population figures that are used throughout the United Nations system.
The World Population Prospect: the 2008 Revision Database provides the most recent data available. Estimates and projected world and country specific populations are given from 1950 through 2050.
Data underlying the population estimates are national and sub national census data and data on births, deaths, and migrants available from national sources and publications, as well as from questionnaires. For all countries, census and registration data are evaluated and, if necessary, adjusted for incompleteness by the Population Division as part of its preparations of the official United Nations population estimates and projections.
2.The International Programs Center at the U.S. Census Bureau, Population Division also develops estimates and projections based on analysis of available data (based on census, survey, and administrative information) on population, fertility, mortality, and migration for each country or area of the world.
For most countries adjustment of the data is necessary to correct for errors, omissions, and inconsistencies in the data. Finally, since most recent data for a single country is often at least two years old, the current world population figure is necessarily a projection of past data based on assumed trends. As new data become available, assumptions and data are reevaluated and past conclusions and current figures may be modified.
For information about how these estimates and projections are made by the U.S. Census Bureau, see the Population Estimates and Projections Methodology.