I don't know about statistics but it seems to me that turbine aircraft are designed with all kinds of redundancy to improve safety and a lot of this gets undone by operating with one pilot. The pilot is the most important safety feature in the aircraft and if he/she is alone and becomes incapacitated or makes a mistake that could have been caught by another pilot the passengers are in trouble. Why would you want to have two of everything else but only one pilot? Cost is obviously the reason but it seems to me that if you can't afford to put two pilots in an expensive, all-weather turbine airplane you really can't aford to operate the airplane. I see no reason why my passengers should die because I have a coronary or other catastrophic problem.
Professional pilots who agree to fly these airplanes single pilot set a bad precedent and give operators the idea that it's cheaper to operate these planes than it really is. The poor passengers don't know any better and they trust the operators assuming that one pilot must be as safe as two or the FAA wouldn't allow it. I've always been surprised that the insurance companies allow this.
Sorry for the rant, I know I didn't help answer your question it's just that everytime I see an expensive turbine business aircraft flown by a single pilot at an FBO it strikes me as a potentially serious reduction in safety to save a few bucks. I've flown a lot of Part 121 through a lot of bad weather and problems/emergencies and I know that there were plenty of times when the operation would have been far less safe if there were only one of us in the cockpit. Single pilot passenger operations with high performance turbine aircraft in high workload airspace is simply an example of cutting corners to save money...period. I hope you are looking for these statistics to encourage an operator that two pilots are safer than one.