Rachel Glennerster is a professor of economics at the University of Chicago, which is more-or-less the dictionary definition of an academic economist. But earlier in her career, she worked as a policy economist at the UK Treasury, the IMF, and the the UK Foreign, Commonwealth & Development Office, which focuses on topics of international economic cooperation and foreign aid. When it comes to distinctions between academic and policy economists, she knows whereof she speaks. In a blog post back in 2014, she summarized the distinctions with this table.
There are some economists who can move fluidly between the academic and the policy world. But the table helps to explain why many don’t make the jump very well, or prefer not to try.