From the National Bureau of Economic Research: History’s Masters: The Effect of European Monarchs on State Performance

The pdf is here. I guess I'm curious about both this text and texts like it more generally.

In the abstract, they note:

We code the degree of blood relationship between the parents of rulers. The ‘coefficient of inbreeding’ is a strong predictor of ruler ability, and the corresponding instrumental variable results imply that ruler ability had a sizeable bearing on the performance of states and their borders.

What do you or others think about this sort of quantitative methodology? Is it the sort of thing historians would be familiar with?

And finally, are the findings in this paper (or papers like it) accurate? How are they received by historians?