The data on that page isn't loading for me but either you're interpreting the data too naively or their study is missing some very important factors. With zero

The data on that page isn't loading for me but either you're interpreting the data too naively or their study is missing some very important factors. With zero cost (money or otherwise) to enroll in a course the number of students who will sign up should be ridiculously inflated. There are people who just want to get their feet wet and try the first few assignments, some who just want to download all the videos, etc. Even if you only measure the people who did all the assignments or exams it's still not a direct comparison to a traditional classroom because there are: no curves (yet– though a few courses drop the lowest assignment grade), a hugely diverse student body without any verified qualifications/prerequisites, varying English (or other) abilities, etc. Characterizing the completion rate as 'absymal' suggests that the number is intrinsically significant which really isn't the case outside of a traditional school– where the enrollment pool is already carefully filtered and there is external pressure to keep rates at some arbitrary level. Edit: Forgot to refresh before submitting my reply so this is repeating some things which have already been said.