That is a new and highly useful book by Stuart J. Hillmon, here is one bit from it:
Truthfully, majoring in economics is not really all that helpful for your admissions prospects. This is true for two reasons. First, knowing who does well in undergraduate economics is not terribly helpful in identifying who will be a good academic economist. Unlike other fields such as chemistry or physics, what happens in undergraduate courses bears little relation to what happens in graduate courses. For this reason, the committee cannot predict how well you will do as an academic economist based on your doing well in your undergraduate econ courses. Consequently, they don’t give too much weight to your stellar performance in the usual undergraduate classes.
For this book, I would have asked for greater length, more discussion of government and private sector careers, and more discussion of non-orthodox paths through academic economics, or for that matter seeking employment at a teaching school or attending a Ph.D. program below the top tier. You will note “Stuart J. Hillmon is the pseudonym for an academic economist who graduated from a top five doctoral program in economics and currently teaches courses in policy and economics.” The book is structured accordingly and perhaps that will frighten some of you away. If everyone were like Hillmon, I would not myself today be an economist.
Still, this is a good place to start if you are considering whether to get a Ph.D. in economics.