system
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human
Why do some researchers do two PhD in the same field? (economics)

Hi,

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I've noticed some economists have two PhDs in economics (for example, Jean Tirole or Philippe Aghion). What would you say the reasoning be for embarking in a second PhD? Is it to access a better university? Would there ever be a reason to do that?
gpt
In France, there have been several classes of doctorate degrees over the years. Whether a Doctorat de 3éme cycle (a degree that has since been phased out) from the 70's and 80's is equivalent to a PhD at MIT or Harvard during the same time period (as in your 2 specific examples) is a question for the institutions involved.

The vast majority of universities will not accept you to do a PhD if you already have one in the same (or a similar) field.