It has demonstrated that there are far too few accidents caused by pilot licensing and training issues to pick up even quite substantial improvements (or deteriorations) by counting accidents and incidents in a single year.
I take the thrust your point in principle. However the data was collected over all seven years of post JAA operations and not just a single year, and therefore the maximum amount of data available was presumably used. One could argue that if seven years is not enough then how about ten, or fifty or whatever. I accept that there are few incidents from which to enable large statistical sampling, but what has been done appears to the best possible from such low numbers, which in themselves might be argued are further evidence of unnecessary over regulation