  An online auction waterfall for an ad impression may contain auctions that
are unlikely to result in a winning bid. Instead of always running through the
full auction sequence, one could reduce the transaction cost by predicting and
skipping these auctions. In this paper, we derive the auction abort rule that
maximizes the net income of the waterfall under certain conditions, knowing
only the publisher tag of the current auction and the ad request context. The
net income is defined as the payoff (revenue) minus the transaction cost. We
translate the abort rule into a purity measure and propose a corresponding
split criterion for a decision tree. Training and testing on randomly sampled
data indicate that the abort decision tree performs better than the full
waterfall and the abort rule that makes use of only the publisher tag feature.
When the transaction cost is higher, the cost saving, and thus net income gain,
is higher for either abort decision rule.
