Area of specialization

In the online admission application, I am asked to describe area of specialization. To what does this refer?

If you already have specialized areas of interest in economics that you would like to list or discuss, that question gives you the opportunity to do so, in 350 words or fewer. If you do not yet have any specialized areas of interest in Economics that is OK, and you can leave that part blank. The Graduate Handbook lists specialty areas within the Ph.D. program.