The calculated N2 and N2 of Cmcm SnSe at 300 K is shown in Fig. , and equivalent plots for all ten systems are provided in the ESI. † In general, collisions are dominant at low frequencies up to around 2 THz, above which phonons have sufficient energy to access decay pathways, which become competitive with collisions from ∼2-3 THz and dominate at higher frequencies. The total number of scattering pathways also generally increases considerably at frequencies approaching the maximum frequency f max in the phonon spectrum. With reference to the cumulative κ iso in Fig. , which indicate that the majority of the thermal transport occurs through modes with f λ < 3 THz, this analysis shows that the averaged lifetimes are limited mainly by collision processes, and, assuming similar interaction strengths, that transport through the higher-energy modes may be limited by a larger scattering phase space.