Rocco Molinari Rocco Molinari Livia Elisa Ortensi Livia Elisa Ortensi University of Krems Press 2025 Key points • Irregular migrants are difficult to capture in statistics because of their absence from official sampling frames, mobility, and fear of detection. Surveying them requires tailored approaches, including non-probability sampling, trust-building strategies and ethical safeguards. • This chapter reviews three types of surveys that can yield data on irregular migrants: those that explicitly include them in the sampling design, those that target applicants of regularisation programmes, and retrospective surveys that reconstruct past legal trajectories. • Drawing on examples from France, Italy, Spain and the United States, this chapter shows how innovative designs and context-specific adaptations can improve coverage and data quality. • Each approach has its own strengths and limitations. A combination of methods, applied thoughtfully, is needed to strengthen the evidence base and support more accurate data collection and analysis. PDFDocument eng 2025-09-30T11:25:54.697923Z 2025-09-30 Surveying irregular migrants hard-to-count-population sampling methods Legal status trajectories Data challenges Mixed methods 372284 b application/pdf http://creativecommons.org/licenses/by-nc/4.0/