The 2008 revision of the United Nations world population prospects: challenges in estimating and projecting the world’s population

Gerhard K. Heilig, United Nations
Nan Li, United Nations
Vladimira Kantorova, United Nations Population Division
Pablo Lattes, United Nations Population Division
Taeke Gjaltema, United Nations Population Division

The United Nations Population Division has prepared global population estimates and projections since 1951. The 2008 Revision of the World Population Prospects (WPP) provides a broad range of demographic indicators for all countries of the world, all development groups, and major geographical regions -covering the period from 1950 to 2050. This paper outlines some of the problems of estimating population trends for the World Population Prospects. There is still a significant number of countries where demographic information is incomplete, outdated, seriously distorted or almost completely lacking. This paper discusses the procedures and models that are used to derive plausible and consistent demographic estimates for countries with highly deficient or unreliable empirical data. In particular, it provides examples for estimating child mortality from different data sources, including various demographic surveys. The paper also outlines procedure of inter-censal and regional consistency checking, which are essential for the validation of WPP population estimates.