Studies of migrant transnationalism are dominated by qualitative case studies. To take the field further, there is a need for more quantitative studies and for connecting quantitative and qualitative studies through a reiterative feedback loop. In order to contribute to this, we take two refined and original quantitative studies, one by Snel et al. and one by Portes et al., as a vantage point, commenting on the authors’ organization of analytical categories and their operationalization of key concepts, in light of our own, qualitative data. These data come from a research project, EUMARGINS, where we analyze processes of inclusion and exclusion of young adult immigrants and descendants in seven European countries, using participant observation and life-story interviews in combination with statistical data. We conclude that the process whereby young migrants identify themselves in terms of ethnicity and belonging is context-specific, multidimensional, and hard to study quantitatively.