This is the 1% of cases. As I understand it, most branches take the same path most of the time. Think of a loop for instance. With purely statistical prediction

This is the 1% of cases. As I understand it, most branches take the same path most of the time. Think of a loop for instance. With purely statistical prediction (go whichever direction the branch takes more often), loops will be predicted with extreme accuracy and the result is a huge number of correct branches. Then think about error handling code which isn't triggered most of the time due to input being valid. Between these two easy cases, I think you cover the majority of branches is programs which is why so many of them are predictable.