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...

Food consumed outside the home in restaurants or other food establishments is a growing segment of consumption in many developing countries. However, the survey methods that are utilized to collect data on expenditures on food away from home are often simplistic and could potentially result in...

In a randomized control trial, the precision of an average treatment effect estimator and the power of the corresponding t-test 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...

The aim of this paper is to introduce a practical nonlinear generalization of PCA that captures nonlinear forms of dependence and delivers truly independent factors. The output of the method is a low-dimensional curvilinear coordinate system that tracks the important features of the data. The...

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...