János Köllõ studied economics at the Budapest (then Karl Marx) University in 1972-77. He has a doctoral degree in sociology (1980) and a "candidate's degree" (Ph.D.) in economics (1990). Employed as a full time researcher at the Institute of Economics of the Hungarian Academy of Sciences (1977-92, 1994-) and Collegium Budapest Institute for Advanced Study (1993-94), he has been engaged in the analysis of labor markets and industrial relations. He published several papers on the transformation of Central and East European labor markets in the post-communist period. János Köllõ is Fellow of the William Davidson Institute, Ann Arbor (1997).
He joined IZA as a Research Fellow in October 2000.