I am currently an undergrad in a top 50 department. From what I see, I think the attrition rate is about 10-15%(at most 2 will leave the program, out of 15). I will be going to a top 30 department next fall and is horrified by its attrition rate. From what I heard, the attrition rate is about 33%(Although the coordinator says it's only about 20%, 20% still sound very high). Moreover, Out of 20 from one particular year, 8 were left. This rate is much higher than my perception. I am wondering if the attrition rate is higher in better departments? Please share attrition rate in top departments so I will have some idea and be more relaxed/horrified.
Edit: Here I am only taking about the attrition rate for the prelim.