Assessing the Feasibility, Scalability and Validity of Innovative Methods for Estimating Irregular Migration

This working paper presents an assessment of the feasibility, scalability, and validity of estimates of irregular migration stocks and flows, based on six pilot studies conducted within the framework of the MIrreM project. The pilot studies made innovative use of 1) flight passenger data, 2) social media data, 3) mortality register data, 4) register health care data, and 5) labour force surveys. We examine the key dimensions of each of these three concepts and evaluate how they apply to each pilot study. With one exception, all studies were found to be feasible. Several also demonstrated scalability; however, limited data availability across different geographic contexts or time periods remains a significant challenge. Validity, in particular, continues to be the most elusive component due to the absence of a definitive reference standard. Nevertheless, the estimates produced showed a notable degree of alignment with existing data sources and, in some cases, a non-negligible level of internal consistency across countries when comparable estimates were available. Overall, the pilot studies represent a meaningful step forward in the empirical study of irregular migration, offering promising methodologies that warrant further development and replication.