Percent of People in Each Grade in A.'.A.'.
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No absolute numbers (especially if you're counting across all possible lineages, legitimate and illegitimate etc.).
But, among the reasons that a pyramid is used as a symbol of initiation is that it's a reasonable diagram of grade distribution - with significant reduction at each tier.
Crowley said 100 years ago that something like 1 in 8 Probationers made it to Neophyte. The numbers are better today, but there is still significant loss along the way. And I suspect that the overall number of 1=10s making it to 2=9 is around 50%.
And so forth.