Currently, the industry of arboriculture is the 5th most dangerous industry in the US according to deaths per 100,000 workers. However, the most common injury or fatality is not from climbers, it is from people being struck-by or hit by objects on the ground (ie. chainsaws, falling trees, branches etc.
). Of tree climbing injuries, being struck by a chainsaw or falling are the two highest ranking categories. Furthermore, when injuries are sustained, they are usually severe and require medical services care.
As far as climbing is concerned. When injuries happen they are also from struck-bys or exposure (electrical). Research results are sketchy for climber accident data. This can be helped by better recording and data collection by tree care companies when any accident occurs, even if it is a scrap that needs a band aid.
The rest of this information and more can be found my reading a thesis published last year by Shane Vosberg and Dr. John Ball at South Dakota State University. That is the source of this information.
Proper accident prevention and safety training comes from proper recording and reporting of accidents. Please take the time to report and record and accidents that happen in your company.