Why are there discrepancies between The World Factbooks demographic statistics and other sources?
Although estimates and projections start with the same basic data from censuses, surveys, and registration systems, final estimates and projections can differ as a result of factors including data availability, assessment, and methods and protocols. Data availability Researchers may obtain specific country data at different times. Estimates or projections developed before the results of a census have been released will not be as accurate as those that take into account new census results. Assessment Researchers can differ in their assessment of data quality and in their estimates based on the available country data. They often need to adjust their estimates due to such factors as undercounting in a census or underregistration of births or deaths. Methods and protocols Differences in methods and protocols can shape the way estimates and projections are made of fertility, mortality, and international migration, and how these data are integrated with the population data. For example, the
