lifetime of grades?
Please forgive my ignorance. Looking at the BFTA Grades site it appear that the grades are averaged over 20 results. Is there any time duration for those scores? If not then there may possibly be some AAs who are maybe not so currently in-grade? That may account for the number of AAs, etc. Equally a C grade will take quite a long time to transition to A, AA until a lot of the learning curve scores age out? So it could well be that a C ends up shooting too well for C or even B.
Changing that system might (I don't know the details) be a lot of work but if the data (score and date) was stored in a database rather than a spreadsheet it would be perhaps better to have grades based on 12 months or 24months (pick a number) which could change the grades without changing the boundaries or setting bands based on percentages (e.g. top 25% = AA, etc).
I am happy to offer my help with the computer side of things if anyone needs some help.