Mathias is leading an interdisciplinary research group focusing on the drivers and dynamics of international migration processes and their impacts. His wider research interest is to understand the role and relative importance of migration policy in shaping patterns of international migration. His publications include The Political Economy of Refugee Migration and Foreign Aid (Palgrave, 2009), and he has published in numerous journals such as Demography, Population and Development Review, International Migration Review, European Union Politics, and the Journal of Peace Research.