Hard-to-reach population groups in administrative sources: main challenges and future work

The paper deals with the concept and the definitions of hard-to-reach groups and the ways of capturing them in administrative sources, providing a detailed discussion of the meaning of hard-to-reach in the context of administrative sources and in relation to the traditional hard-to-count groups in censuses and surveys. The review of country practices shows that hard-to-reach populations in administrative data can be interpreted in different ways and that their definition is dependent on countries’ circumstances, though there are two main reasons for identifying a group as hard-to-reach in administrative sources. One of the interpretations is selecting some groups, typically considered difficult to reach with traditional survey methods (such as homeless, illegal immigrants or indigenous people) and then trying to capture them in registers to overcome the challenges of traditional field collection or to get more complete information. At first glance, administrative data might offer the potential to improve frame coverage for some target populations, but may also lead to other hard-to-reach or “hidden” populations for different population groups. Indeed, another interpretation refers to the incompleteness of registers or linked administrative databases, which makes some groups, such as children or elders, hard-to-reach and hence describe with data, due to time lag in reporting of some events or to other accuracy problems with the source itself. The paper summarizes the experience of national statistical offices in accessing hard-to-reach groups and describes problems and challenges in capturing them. It also proposes further possible work to improve access to hard-to-reach groups using administrative data.