Comment by tsimionescu

I don't know, since they unfortunately don't cite a source for that number, but I can imagine some sources of data - insurers, vehicle repair and paint shops. Since average miles driven without incident seems plausible to be an important factor for insurance companies to know (even minor incidents will typically incur some repair costs), it seems likely that people have studied this and care about the accuracy of the numbers.

Of course, I fully admit that for all I know it's possible the article entirely made up these numbers, I haven't tried to look for an alternative source or anything.