Measuring irregular migration and population flows – what available data can tell.

Wild assumptions, estimates and number games are made in regard to irregular migration flows. While the numbers cited are, in fact, often dated and of unclear origin, reports use such numbers to suggest a rise in irregular migration; they also usually assume that irregular entry and, to some extent, overstaying are the only significant pathways into irregularity. To properly account for irregular migration flows, however, both in- and outflows, as well as the complex ways of becoming (or ceasing to be) an “irregular migrant”, have to be included. Thus, apart from irregular migration flows in the narrow sense, like unlawful entry and emigration of persons (unrecorded returns, registered voluntary returns and deportations), other flows – notably status-related inflows (overstaying, withdrawal of residence status, rejection of asylum claims), status-related outflows (regularisation, ex lege changes of the legal status of irregular migrants, etc.) and flows related to vital events (births and deaths), must be considered. The article provides a critical appraisal of available data sources, indicators, estimates and methods to estimate irregular migration flows. In the context of a case study, we then analyse statistics of apprehensions at the EUROPEAN UNION’s external borders in Eastern Europe as indicators of geographical flows -- migration flows in the narrow sense -- arguing that despite the many limitations of the available data, the data can nevertheless be used as indicators of certain trends.