Though the lineshape of σ i is complex, knowledge of ω res,i and W i is sufficient to deduce how σ i contributes to σ(ω). For Drude nanoparticle dispersions, MPM predicts that the ensemble extinction spectral linewidth shows a pronounced nonmonotonic trend with η, and the magnitude of the broadening depends on the strength of interparticle attractions and whether quadrupoles are included in the calculation. However, the average of the single-particle spec-tral linewidths ⟨W i ⟩ is insensitive not only to volume fraction, but also to attraction strength and moment truncation level (Figure ).