You're looking at a chart from Stephen Pettigrew's look at 11 million brackets yesterday
That spike represents about 156,000 people who decided to submit a bracket with nothing but favorites advancing, all the way through the tournament. Since only one 1-seed made it through to the Final Four (Florida) and it lost, this meant that an enormous amount of brackets ended up with the same score, among a field that was otherwise almost perfectly distributed. It's not even that picking all chalk is that bad an idea—in ESPN, it took you into the 77.6th percentile—but more the fact that it goes against the fundamental idea of picking a bracket being a thing you do for fun.
We asked Stephen to pull a few more numbers, and this is what he turned up:
I looked at who picked all the 1's go to the Final Four (360,935; 3.28%), who picked at least a 12-16 seed to make the Finals, which has never happened (294,036, 2.67%), and who picked a 9 seed or worse to go to the championship, which has never happened (239,218, 2.17%).
The all-1-seeds is a cousin to the all-chalk brackets, but you can make the case for each of the 1-seeds making it on, at least, even if it's just the worst. The people picking low seeds, though, are probably just fans of those schools. There are also the 31,449 people who picked nothing but upsets, who are a whole other story.
Those are varying levels of goofy to misguided, but really, nothing's going to touch 156,000 dummies going full-on chalk.
Read the rest of Stephen's article below.
Chart by Reuben Fischer-Baum