Population estimates and projections are essential for tracking trends in health and socioeconomic development and directing resources to where they are most needed. Yet such estimates may vary among those who provide them, and the reasons for such differences are often unclear. We begin with a review of data sources and methodologies, all of which typically rely on the demographic balancing equation, a means of accounting for population change through births, deaths, and migration. We also identify various providers of population estimates and projections, similarities and differences in their assessments of population change, as well as other relevant issues.

• This technical note is available in English and Arabic.