Researchers in many fields, such as demography, economics, and sociology, have established various data collection methodologies and principles to answer a range of academic and policy questions on migration. Although the progress has been impressive, some basic challenges remain. This paper...

Despite of its relevance for science policy and the scientific community, empirical research on doctoral education in Germany is sparse. The few papers available face challenges in the sampling approach: simple random sampling is not possible, because a universal register of PhD candidates in...

In a randomized control trial, the precision of an average treatment effect estimator can be improved either by collecting data on additional individuals, or by collecting additional covariates that predict the outcome variable. We propose the use of pre-experimental data such as a census, or a...