Je ne sais quoi
Should you include foreign phrases and expressions in English papers? Do they add a certain je ne sais quoi to your writing?
Of course, it is always your prerogative to choose the language and style of your paper. But here's some food for thought.
A changing readership
In the days of yore, it was common (if not compulsory) for people writing in English to casually toss a Latin, French, or German phrase at the reader. Of course, in those days, the group of readers was also narrower.
Happily, readers in economics today are a wonderfully diverse group culturally and linguistically. So if we're throwing in an a priori, is it also OK to throw in a先驗 or a पूर्वसिद्ध?
Expressing the same idea in English
It is often quite simple to replace a foreign phrase with an English one, especially in the Introduction or abstract where the terminology need not be too technical. Here are examples:
à la: as in, like
inter alia: among other things
a priori: prior to, before
ex post/ex ante: after x/before x
vis-à-vis: with regard to
Even if you decide that the idea is best expressed in the foreign language, you can always offer the reader a brief translation within the text using an em-dash (--) or a pair of commas.