Assuming that the MOs transforms like irreducible representations of the molecular point group, then ∆r = 0 for any centrosymmetric system because the charge displacements R ia must preserve inversion symmetry in that case. From a symmetry perspective, this is a feature and not a bug. However, it does mean that charge-resonance states (involving counterbalancing contributions from forward and backward CT) cannot be detected by ∆r. To obtain a non-vanishing metric for centrosymmetric systems, an "electron displacement" measure Γ = ∆r + ∆σ (10) has been suggested. It combines ∆r from eq. 9 with