The amount of electron transfer from an initiator to a monomer for the initiation reaction of anionic polymerization (Delta N) is calculated by means of the regional density functional theory through ab initio quantum chemical calculations, and the correlation of Delta N with reactivity is studied. For each initiator, Delta N increases as the reactivity of the monomer rises. This order of the value of Delta N, moreover, corresponds perfectly to that of the reactivity of the monomer. We reveal the correct order of reactivity of the monomer, which has been hard to account for in terms of the conventional Hammett sigma(p) parameter.