Evidence on how the quality of professors matter

Applied economists have become enthusiatic users of natural experiments to generate exogenous variation in key independent variables although it has been argued that this approach has severe limitations: particular instruments may not identify parameters of interest (see Heckman passim). The paper below I think is quite an imaginative use of a "natural experiment" from a dark period in history to see how the quality of professors matter for their graduate students.

Quality Matters - the Expulsion of Professors and Ph.D. Student Outcomes in Nazi Germany
Fabian Waldinger

I investigate the effect of faculty quality on Ph.D. student outcomes. To address the endogeneity of faculty quality I use exogenous variation provided by the expulsion of mathematics professors in Nazi Germany. I find that faculty quality is a very important determinant of short and long run Ph.D. student outcomes. A one standard deviation increase in faculty quality increases the probability of publishing the dissertation in a top journal by 13 percentage points, the probability of becoming full professor by 10 percentage points, the probability of having positive lifetime citations by 16 percentage points, and the number of lifetime citations by 6.3.