Percentage of collision direction is going to be EXTREMELY subject to local riding conditions.

On the route I ride, it would be almost impossible for someone to hit me from the front. I'm riding miles and miles down high speed roads with very rare driveways and intersections.

On routes in cities that involve a lot of pull-outs and left turns, I'd imagine that being hit from the front or being pulled out in front of would be much more common.

There's just no way that a single number can quantify risks for all cyclists. You could probably create a stat that indicated that 80% of all bicycle accidents were caused by protruding tree roots if you sampled the right cyclists.