  This paper re-examines the Shapley value methods for attribution analysis in
the area of online advertising. As a credit allocation solution in cooperative
game theory, Shapley value method directly quantifies the contribution of
online advertising inputs to the advertising key performance indicator (KPI)
across multiple channels. We simplify its calculation by developing an
alternative mathematical formulation. The new formula significantly improves
the computational efficiency and therefore extends the scope of applicability.
Based on the simplified formula, we further develop the ordered Shapley value
method. The proposed method is able to take into account the order of channels
visited by users. We claim that it provides a more comprehensive insight by
evaluating the attribution of channels at different stages of user conversion
journeys. The proposed approaches are illustrated using a real-world online
advertising campaign dataset.
