Measuring Irregular Migration: Innovative Data Practices

IOM’s Global Migration Data Analysis Centre organized a workshop to discuss innovative data collection practices on irregular migration, with support from the UK Department for International Development (DFID). The event represents a follow-up to a previous workshop held in Nuremberg (Germany) in 2016, also supported by UK DFID, focusing on the measurement of “safe migration.” This year’s workshop brought together experts from the governments, academia, international and non-governmental organizations, providing an opportunity to:

a) Learn about recent initiatives to improve qualitative and quantitative data on the size and dynamics of irregular migration, particularly in the European context.

b) Exchange practices to estimate stocks of irregular migrants, with a focus on Europe and a comparison with the U.S. context.

c) Propose solutions to the challenges of disaggregation of data by migratory status when such status is irregular.

d) Discuss how to improve understanding of the specific vulnerabilities of migrants travelling irregularly – whether assisted or not by smugglers.

e) Explore how to gather more data on migrants in an irregular situation – their numbers, profile, needs, and access to services. 


Presentations given at the workshop are available below.

Introduction: Irregular migration data in light of the SDGs and the Global Compact on Safe, Regular and Orderly Migration

Frank Laczko, IOM’s Global Migration Data Analysis Centre

Session 1: Measuring irregular migrant stocks: examples from the U.S. and Europe

Jeffrey Passel, Pew Research Center, Estimates of unauthorized immigrants in the U.S. and their characteristics

Georges Lemaitre, formerly at OECD, A general method for estimating the size of the irregular migrant population based on traditional data sources

Session 2: Measuring irregular migration flows: innovative quantitative and qualitative methodologies

Linnea Lue Kessing, Danish Refugee Council (DRC)

Vivianne van der Vorst, IOM’s Displacement Tracking Matrix (DTM)

Session 3: Migrants in vulnerable situations and access to services

Eliza Galos, IOM’s Migrant Assistance Division

Luigi Achilli, Migration Policy Centre, European University Institute


  • The workshop summary report is available here.
  • Access the agenda here.


Note: This workshop is funded by UK aid from the UK government; however the views expressed do not necessarily reflect the UK government’s official policies.