ACP has posted more statistics about PBP and the results are in: the 84-hour group had the lowest DNF rate of the sizable groups, at 18.5 percent. As a fan of the 84-hour start, I was gratified to see this result. I’ll be the first to admit we did not have the rain storms endured by the 90-hour and 80-hour groups on the first night, nor the long lines at the outbound controls, so in that respect it is not an apples-to-apples comparison.
The 90s, overall, had a dropout rate of 29.4 percent, and the 80s had a rate of 28.1 percent. The smaller 84-hour “special bikes” group of 41 bikes had the lowest rate of all, at 10.4 percent, and the special 90-hour group had a 36.8 percent rate.
The overall DNF rate was 27.7 percent, which does not include DNS (did not start).
See all the statistics Here
The Daily Randonneur 
What I find interesting is that how low the “out of time” rate is for the 84-hour group–1.4% vs. 2.5% for 90-hour and 3.1% for the 80-hour group. I’m not a statistical wizard, so I wouldn’t pretend to assert that the lower rate in the 84-hour group is the result of anything other than sheer chance, but it would suggest that those who suffered through the rainstorms of the first night did have a worse time of it. There are other alternative explanations, of course. It’s also difficult to tell how many of the DNF group packed because they didn’t feel they could make the next control in time, which is the sort of thing you can’t draw conclusions about without qualitative research (e.g. surveys).
Not to geek out about this or anything …..
Speculations regarding observed DNF rates:
Most of the 84hr starters I’ve come across are quite confident they will make the time limit. Riders that are worried about the time limit tend to pick the 90hr start and a number of 90hr starters have been doubtful they will finish at all. Some 80hr starters are focused on ‘doing a time’ and pull out when they aren’t going to make their target, even if they are likely to finish in time.
Dave mentioned “Riders that are worried about the time limit tend to pick the 90hr start” which is quite right but lets not forget those riders who could easily complete the PBP within 84 or even 80 but dont because it is so much fun – what’s the rush.
bicycletim