Are you certain those numbers are being reported by AA? In any case, the original A.A. shared something much different:

"Of alcoholics who came to A.A. and really tried, 50% got sober at once and remained that way; 25% sobered after some relapses, and among the remainder, those who stayed on with A.A. showed improvement. Other thousands came to a few A.A. meetings and at first decided they didn't want the program. But great numbers of these -- about two out of three -- began to return as time passed." (Foreword to Second Edition)