According to this, a Tesla driver gets in an accident only a quarter of the time compared with the average car/driver (probably similar to other modern cars with advanced safety features), and when Autopilot is engaged, it’s even less likely to be in an accident by a factor of nearly two.

It can be argued that Autopilot is more likely to be used in situations where crashes are less likely: slow speed crawl, long & straight sections of highway, etc.