Most entry and mid -level jobs are offered as either so-called short term (STC) or extended term contracts (ETC). In the case of the former (the most ubiquitous), you are essentially utilized as staff, but are considered a "contractor" for remuneration purposes. STCs receive no benefits, and have to be sure to negotiate a good "daily rate" to avoid being underpaid. ETCs receive some health care and limited paid vacation. Job security is an issue with STCs as the duration of these contracts can vary from just a couple of days to 150 days. In fact, the maximum one can work at the Bank as an STC is 150 days per fiscal year, which means that you either have to take a very long unpaid vacation, take many small unpaid vacations, or find employment for the remaining months. It's also very important to find managers who are willing to mentor you, as it is easy to feel lost in the Bank and training opportunities are limited for STCs.
This picture is entirely different for staff positions (or programs such as the JPA or YPO), but these are very competitive and exceedingly difficult to come by. That said, the best way to get these positions is by starting off as an STC, working hard, and becoming skilled in the art of "Bank politics."
One more thing to consider is that Americans have to pay normal taxes over their earning, whereas foreign nationals don't have pay income tax at all. As a result Americans are discriminated against, either in terms of net pay, or if the gross pay is adjusted accordingly, in terms of opportunities since managers will be hesitant to hire "more expensive" Americans.
