Do you need a predoc to apply?
Predocs have become quite common among PhD applicants. Based on our multi-year experience as admissions chairs, we wish to convey that a predoc experience is not necessary to apply to Northwestern. In fact, it need not improve your chances of being admitted.
You might enjoy the experience, but it is not clear whether it helps in your transition to independent research. We see hundreds of recommendation letters per year. These indicate that many, if not most predocs, entail largely mechanical work – literature review, data cleaning and handling, using specific programming languages, etc. These are useful, but basic technical skills that you will quickly learn in graduate school anyway. This type of experience does not really make your application stand out.
How valuable are recommendation letters from predocs? Do they improve your chances of being admitted to Northwestern? Naturally, this depends on your other letters. However, we find that these letters are typically not very informative for our purposes. These letters are not very informative. First, the mechanical nature of most predoc chores does not allow you to showcase your creativity, economic insight, and communication skills, which are the attributes we value the most. Second, we rarely see weak recommendation letters from predocs. As admissions chairs, we understand that recommendation letters are part of the compensation package—and weigh them accordingly.
Bottom line: If you are interested in the Economics Department at Northwestern, we encourage you to apply before, or simultaneously with, your predoc application, and then decide. While there are no guarantees of admission (we admit about 11% of all applicants), recent experience tells us that a predoc does not necessarily improve the odds.