The United Nations population estimates and projections form a comprehensive set of demographic data to assess population trends at the global, regional and national levels. They are used in the calculation of many of the key development indicators commonly used by the United Nations system, including for more than one third of the indicators used to monitor progress towards the achievement of the Sustainable Development Goals. The 2019 revision of the World Population Prospects is the twenty-sixth edition of the official United Nations population estimates and projections, which have been prepared since 1951 by the Population Division of the Department of Economic and Social Affairs. The 2019 revision presents population estimates from 1950 until the present for 235 countries or areas, which have been developed through country-specific analyses of historical demographic trends. It builds on previous revisions by incorporating additional results from the 2010 and 2020 rounds of national population censuses as well as information from vital registration and recent nationally representative household sample surveys. The 2019 revision also presents population projections to the year 2100 that reflect a range of plausible outcomes at the global, regional and country levels. These Highlights summarise key population trends described by the estimates and projections presented in World Population Prospects 2019.

The population and housing census is part of an integrated national statistical system, which may include other censuses (for example, agriculture), surveys, registers and administrative files. It provides, at regular intervals, the benchmark for population count at national and local levels. For small geographical areas or sub-populations, it may represent the only source of information for certain social, demographic and economic characteristics. For many countries the census also provides a solid framework to develop sampling frames. This publication represents one of the pillars for data collection on the number and characteristics of the population of a country.