the one who has won the most first places in the stages; if it's a tie, then second places; third places...
newcomers are irrelevant - the absolute leader is competing with everyone (or almost everyone) in all the stages, and, with all due respect to the newcomers, this should play a significant role...
Not a bad suggestion, but there's one BUT: If you win 4 stages in a row, what's the point of anyone playing the remaining 3 stages, as the AL (Absolute Leader) is already determined. Although the probability of this happening is low, it exists.
Sincerely, K0Lb@zzeR.