All over the world, people are moving. As they always have throughout human history, people today migrate in search of better opportunities, to escape hardship or conflict, or to connect with loved ones. Today, though, the scale of migration is unprecedented and the reasons ever more diverse –great swathes of humanity embark on long and dangerous journeys to flee poverty, conflict, terrorism or the effects of climate change, often seeking refuge or the chance of a better living in countries with stronger economies or more stable politics.

Coping with such movements is challenging in many ways. But a crucial step in ensuring resilience in the face of these challenges is gathering data. Knowing the size of these movements of people, how many enter each country, how many are already there, how old they are, what skills, professions, languages, health and housing needs they have – all of this is essential if countries are to maintain the dignity and rights of migrants while preserving peace and justice within communities affected by migration.

Recognizing this need, the Global Compact for Safe, Orderly and Regular Migration – a political agreement that is expected to be adopted by UN Member States in Marrakesh in December this year – calls on countries to ‘collect and utilize accurate and disaggregated data as a basis for evidence-based policies’.  Of 23 objectives in the Compact, this is the first, reflecting its indispensability if the others are to succeed.

Yet measuring migration is fraught with challenges. People move quickly, sometimes without documents, sometimes fearing the consequences if they are counted. Others simply have no incentive to report their arrival or departure, so they may never be recorded.

Statistics on migration have had to evolve rapidly to keep up with these growing difficulties. Combining information from a variety of sources — immigration authorities, censuses, surveys and population registers, tax offices, education records — holds great promise, and will be a central topic of discussion at this week’s UNECE-Eurostat Work Session on Migration Statistics (24-26 October), a gathering of more than 90 expert migration statisticians and producers of administrative data on migrants.

Effective integration of multiple data sources, few of which are designed for producing migration statistics, requires strong coordination between national statistical offices, migration authorities and other agencies responsible for data collection. The Work Session will bring together representatives from all these groups to promote dialogue and mutual learning.

Emilio Zagheni, director of the Max Planck Institute for Demographic Research, will deliver a keynote speech highlighting research findings on using ‘Big Data’ for migration statistics, while Germany and the United States will share experiences of novel ways to measure asylum seekers and refugees.