Have any studies been done on diving accidents to determine which agency has more accidents?
The simple answer to your question is, 'No'. Comparative rate data are not directly available. A number of individual agencies may collect diving accident data, usually on their own safety history (and, primarily, only data on accidents occurring during training), and such information may be available in various summaries.
The challenges associated with collecting outcome data on diving safety are not unlike those associated with collecting outcome data on health care, education, and similar fields. It is expensive, it is time-consuming, it is best coordinated by an independent / third party, and a reasonably effective and efficient mechanism must be available to allow for post-intervention follow-up. Unfortunately, diving accident reporting is neither complete / comprehensive, nor uniform - far from it. The question, 'what is the health status of a patient 1 year after a procedure' is actually much easier to determine than 'what is the status of an open water diver 1 year after certification'. Because of the nature of funding of health care, there is much keener interest in answering the question about patient status (and a much better system of record keeping to support answering the question), than there is about diver status.
So, just as with many other fields of endeavor, where outcome data are not readily available, surrogate markers based on structure - do agencies subscribe to WRSTC - and / or process - as one example, do agency trainees demonstrate swimming competency during training - are used. And, as you can see from the comments already posted, there is a lack of consensus on the meaning of something as simple as whether an agency subscribes to the WRSTC.
What you are often left with instead of objective safety data is subjective - XXX agency is bigger and therefore better, or YYY agency is smaller and therefore better - or of questionable meaning - 'I require my students to swim in salt water backwards, with their mask off, for 200 yards while solving a Rubik's cube, because that is what makes a good diver'. I do that, so my students are safer.
I am looking for an agency that has safety as a top priority and understand that it seems that it would be instructor and student driven.
I am unaware of an agency for which safety is not a top priority, notwithstanding all the comments about marketing, revenue, etc. I do think different agencies approach at least some aspects of diver training in different ways, and finding out what is the best fit for a student diver is possibly more feasible than trying to determine which agency has the best safety record.
