Here is Anil Hira:
This article examines more carefully the oft-made hypotheses that (1) "technocrats" or politicians with an economics background are increasingly common and (2) that this "improvement" in qualifications will lead to improvements in economic policy. The article presents a database on the qualifications of leaders of the world’s major countries over the past four decades. The article finds that while there is evidence for increasing "technification," there are also distinct and persistent historical patterns among Asian, African, Middle Eastern, and Latin American leaders. Using statistical analysis, the article finds that we cannot conclude that leadership training in economics leads to better economic outcomes.
Here is the (only temporarily non-gated) link, thanks to Bill Evers for the pointer. There is also an article in the Chronicle of Higher Education on this work, I am told. The natural defense of economists, which I will not attempt, is to cite selection effects for which economists achieve public office, and what they must do to rule.
I am happy to admit that governing is most of all about building viable coalitions (more than having good policy knowledge, at many margins), and that we economists are not especially good at that. So I don’t find this result a surprise.