Recently, Mathet, Widlöcher, and Métivier (2015) introduced the new coefficient γ, which relies on different assumptions from the αs and thus better corresponds to computational linguistics annotation efforts.
whereas αs rely on the number of intersections between any pair of units from different annotators, γ builds and relies on an alignment between units that ultimately says which unit from one annotator corresponds to which unit from another annotator, if any.