You’re right. My previous answer was too vague to be useful. Why is it too vague?
Well, obviously first one has to read every single hagiographical miracle report in existence, as well as every Vatican saint investigation report which contains reported miracles. Obviously this will mean reading a lot of Latin and Greek. It will probably take at least a hundred man-years, so it would obviously be useful to recruit a lot of people. Preferably Italian people already living in Rome, so as to be able to visit non-digitized Vatican libraries and Curial record storage.
(Obviously this Catholic focus would be solely for simplicity’s sake, since of course other Christian denominations also report miraculous healings, as do non-Christian faiths.)
One puts all the results into a database. (And of course one would separate things into whether there is historical verification by eyewitnesses, or if it’s just hearsay, or what have you. Here you could get some help from the Acta Sanctorum folks, the Bollandists. They’ve only been working on their hagiographical collation project since the 1600’s.)
Then one makes a chart of results.
And then one will know for sure, or at least one will begin to be able to accurately define the problem.
Since you are so concerned about these results, obviously you should take the lead in creating this vast miracle project database. Since I doubt you’ll be able to get everyone to work for free, and creating a new religious order is difficult nowadays, you’ll have to think about funding and grants. It would be an exciting project, I’m sure, and a nice way to spend the rest of your life (and those of your kids and grandkids).
Alternately, you will have to settle for some vagueness.