Ph.D. Attrition: How Much Is Too Much? - Do Your Job Better - The Chronicle of Higher Education

I'm pleased to say that of the 23 students in my PhD cohort we have seen the early departure of only two: one because she got the dream job she wanted to get after a PhD, and the other due to academic struggles (more or less). We've been generally supportive of each other, and I think that helps. Unfortunately, that's not the case in every cohort, and in our most recent cohort 3 of 14 students have chosen to leave after their first year. That's not the 50% attrition rate mentioned in the article, but PhD programs are long and inevitably some will not finish their dissertations.