TY  - RPRT
        AU  - Schmandt, Marco
AU  - Tielkes, Constantin
AU  - Weinhardt, Felix
        TI  - Random Placement but Real Bias
        PY  - 2025/Dec/
        PB  - Institute of Labor Economics (IZA)
        CY  - Bonn
        T2  - IZA Discussion Paper
        IS  - 18319
        UR  - https://www.iza.org/publications/dp18319
        AB  - Many studies exploit the random placement of individuals into groups such as schools or regions to estimate the effects of group-level variables on these individuals. Assuming a simple data generating process, we show that the typical estimate contains three components: the causal effect of interest, ”multiple-treatment bias” (MTB), and ”mobility bias” (MB). The extent of these biases depends on the interrelations of group-level variables and onward mobility. We develop a checklist that can be used to assess the relevance of the biases based on observable quantities. We apply this framework to novel administrative data on randomly placed refugees in Germany and confirm empirically that MTB and MB cannot be ignored. The biases can even switch the signs of estimates of popular group-level variables, despite random placement. We discuss implications for the literature and alternative "ideal experiments''.
        KW  - refugee integration
KW  - peer effects
KW  - group assignment
KW  - random placement
KW  - random dispersal policy
        ER  -