I don't have actual statistics I can share, but work in the automotive industry and have talked fairly extensively with insurance companies about data sharing as part of usage based insurance. There are actually multiple predictors of accident-prone drivers. Sharp braking is one, but so are frequent lane changes, insufficient following distance, and abrupt speed increases.

Distracted driving is a bigger issue than all of these, but is very hard to actually detect as a first-order effect with current cabin sensors.