It took me a while to understand this, but I think the long consistent blocks are a sorting artifact. As the observed headlines are bucketed by the hour. You do

It took me a while to understand this, but I think the long consistent blocks are a sorting artifact. As the observed headlines are bucketed by the hour. You don't see the title flip within the hour, you just see the percentage. It would have been more interesting to see the title flipping back and forth, because that would reveal how long those tests last. Less neat though.