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The higher the potential payouts, the higher the curation rewards to be distributed, the higher the vote can be.
My bot aims at keeping a steady ROI, so if he can choose between voting at 100% for a potential efficiency of 115% or voting at 1% for a potential efficiency of 125% (the smaller your vote, the higher the efficiency, that's the formula). So if he currently aims at 120% efficiency, he will vote at 50%.
I'm simplifying but that's the spirit.