2006 to 2024 Senior Fellow at the German Institute for International and Security Affairs (SWP), Head of the Global Issues Research Group and of research projects on German, European and international refugee and migration policy and its foreign, security and development policy aspects, as well as demographic developments. 2011-2014 Advisor to the Federal Ministry for Economic Cooperation and Development (BMZ). 1993-2006 Researcher and advisor at the German Council on Foreign Relations (DGAP) and editor of the Yearbook on International Affairs. 1987 to 1993 Research assistant at the Free University of Berlin.

2001 member of the Independent Commission on Immigration of the Federal Government (Süssmuth Commission) and 2004 member of the Expert Council on Immigration and Integration of the Federal Government (Immigration Council); 2020/21 appointment by the Federal Government to the Independent Expert Commission on the Root Causes of Forced Displacement. Member of various advisory boards.

In addition to the Federal Government and the Bundestag, advisor to Diakonisches Werk, Caritas, UNICEF, UNHCR, International Federation of Red Cross and Red Crescent Societies, International Organization for Migration (IOM), Council for Asia-Europe Cooperation (CAEC), EU Commission, National Population and Family Planning Commission (NPFPC) of the People’s Republic of China, World Bank, Global Forum on Migration and Development (GFMD), International Centre for Migration Policy Development (ICMPD).