To be meaningful, you need at least two numbers: the number of crashes avoided because of software intervention and the number of crashes caused by driver inattention.
I think that two numbers would be deceptive because almost no-one is capable of acknowledging their inattention. If you found at that that 50% of accidents are caused by inattention, but the autopilot is a 20% *worse* driver than someone paying attention, you *know* that everyone would flee from AutoPilot it on the assumption they won't be part of the 50% failing to pay attention.
One of the primary problems is that humans (in general) are incapable of acknowledging the weaknesses that cause accidents, thus making it very hard to take measures that reduce the number of accidents. Splitting the numbers apart would contribute to this problem.