In what countries/programs is a graduate student bonus common? I just learned from this question My professor skipped me on Christmas bonus payment that in some cultures/degree-programs, PhD students get bonuses.
I had never heard of this. However, I'm most familiar only with natural science PhD programs in the US.
What countries/cultures and programs are bonuses common?
How big do these bonuses tend to be compared to salary? (if there's a rule of thumb, or commonly the result of a collective bargaining agreement as stated in one of the comments to the above question)
I do not know how common it is but I remember Germany Ph.D students get Christmas bonus. See this link.
When I was doing my doctorate in USA, I remember my colleague from Germany asking my research advisor for a Christmas bonus. He laughed, then figured out it was customary in Germany and then gave him a tie.