In observational studies, the estimation of a treatment effect on an outcome of interest is often done by controlling on a set of pre-treatment characteristics (covariates). This yields an unbiased estimator of the treatment effect when the assumption of unconfoundedness holds, that is, there...

Robustness and fragility in Leamer's sense are defined with respect to a particular coefficient over a class of models. This paper shows that inclusion of the data generation process in that class of models is neither necessary nor sufficient for robustness. This result holds even if the...

Getreide ist das wichtigste Produkt für die Welternährung und die Weltlandwirtschaft: Etwa die Hälfte des direkten Nahrungsverzehrs, gemessen in Kalorien (1990-92: 51,2 %), besteht aus Getreide, und Getreide ist ein wichtiges Futtermittel. Angebot, Nachfrage, Handel und Preise werden durch...