This report was written by Phillip Connor, Senior Researcher, and Jeffrey S. Passel, Senior Demographer.

Editorial guidance was provided by Mark Hugo Lopez, Director of Global Migration and Demography Research; Neil G. Ruiz, Associate Director of Global Migration and Demography Research; James Bell, Vice President of Global Strategy; D’Vera Cohn, Senior Writer and Editor; and Jens Manuel Krogstad, Senior Writer and Editor.

The report was number-checked by Luis Noe-Bustamante, Research Assistant, and Abby Budiman, Research Analyst. Travis Mitchell and Shannon Greenwood, Digital Producers, produced the report. David Kent copy edited the report.

Throughout the estimation and editorial process, more than 25 European migration experts, including many who were part of the 2008 Clandestino project, were consulted on our estimation methods and our estimates. Migration statisticians at national statistical offices throughout Europe, policymakers and academic researchers were also consulted.

Additionally, the report was formally reviewed by the following external reviewers at various stages of preparation:

  • Christian Dustmann, University College London
  • Catherine Fieshi, Queen Mary University of London and director of Counterpoint
  • Albert Kraler, Danube University
  • Victoria Rietig, German Council on Foreign Relations
  • Anna Triandafyllidou, Ryerson University and former professor of European University Institute
  • Carlos Vargas-Silva, Oxford University
  • Hania Zlotnik, former Director of United Nations Department of Economic and Social Affairs Population Division

Final methodological and editorial decisions reflect those made by Pew Research Center researchers and not necessarily those of reviewers.

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