What we do know (and could know) about estimating population sizes of internally displaced people.

The estimation of population denominators of internally displaced people (IDP) and other crisis-affected populations is a foundational step that facilitates all humanitarian assistance. However, the humanitarian system remains somewhat tolerant of irregular and inaccurate estimates of population size and composition, particularly of IDPs. In this commentary, we review how humanitarian organizations currently approach the estimation of IDP populations, and how field approaches and analytical methodologies can be improved and integrated.