JD vs PhD: My Story

A student emails me a question about my offbeat journey through higher education:

Prof. Mankiw,

Love the blog, I've recently become hooked. I noticed you mention in an earlier post that you spent one and a half years at Harvard Law School before switching to economics and earning your PhD. I guess I'm in a similar situation now....

Anyway, I wanted to ask what ultimately compelled you to pursue economics instead of law, as I've been toiling with that decision myself. Did you intend to do a joint JD/PhD and focus your research on law and economics, or did you decide to leave law school entirely? I'm passionate about both fields and took a risk averse application strategy by applying to both types of programs, but most of the input I've received has been from those who abandoned economics to finish their law degree, not vice versa. If you have any input or advice you could share, I'd be grateful.

Thank you, best regards,
[name withheld]

Let me start by summarizing my own education and early career:

• June 1980: Graduated with A.B. from Princeton
• 1980-1981: First-year PhD student at MIT
• 1981-1982: First-year student at Harvard Law School
• Summer 1982: Worked in law firm as summer associate
• 1982-1983: Took year off to work on the CEA staff
• 1983-1984: Back at MIT, finished PhD
• Fall 1984: Back at law school, finished fall semester
• Spring 1985: Taught micro and statistics at MIT
• Sept 1985: Joined Harvard econ faculty as assistant professor

All this looks random and disjointed, and to some extent it was. But I look back at this period of my life as a time of experimentation, when I was trying to figure out my own tastes and talents. A large part of early life is trying to find your niche in the world. Open-mindedness and experimentation were crucial for me, and I believe they are for many others as well. That will mean some false starts (like spending a year and a half in law school), but those false starts are part of a process of learning about yourself.

To get back to the specifics of the question: My observation is that students who start both a JD and a PhD in econ are much more likely to finish the JD than the PhD. (A related observation is that those who finish both degrees are more likely to be law professors than econ professors.)

For most people, a JD is the easier degree to finish, as it is all course work, and it takes only three years. A PhD is typically five or six years, the second half of which is devoted to original research. By comparison to a JD, a PhD is a long, hard slog. That does not mean it's not worth it: some long, hard slogs end up passing a cost-benefit test. But it does require a greater degree of commitment and enthusiasm on the part of the student to finish the degree.

My case is somewhat abnormal. During my period of experimentation, I learned that I was only a middling law student. By contrast, I got my PhD with only two years of residence at MIT. (I turned back the third year of my NSF fellowship to the US taxpayer, but I won't claim any altruistic motive in doing so--I just didn't need it.) In the fall of 1984, I found myself a so-so second-year law student with a PhD under my belt and a small but growing list of academic publications. It finally dawned on me that my comparative advantage was econ, not law. Remembering the irrelevance of sunk costs, I moved across the parking lot from the Harvard Law School to the Harvard economics department, where I have now been on the faculty for over twenty years.

Update: After reading this post, one of my law school teachers emails me: "too modestly, you described yourself as only a so-so student. I recall you as far better than that."

It is nice to hear that I was a better law student than I recall being. In any event, while in law school, I decided, rightly or wrongly, that I had more natural ability in econ than law. I suspect that, while paying the law school's tuition, I spent more time writing econ papers for academic journals than studying the law books. That fact made me realize I was probably sitting in the wrong building on the Harvard campus.

Update 2: More on my story.