Abundance ratios (log[X(PAH)/X]) between the models with and without PAHs as a function of density. The ratios were calculated at the best-fit ages estimated through Eq. (B.1). The filled points, empty points, and crosses indicate the species in TMC-1 CP and L1544 that prefer the model with PAHs, prefer the model without PAHs, and have a non-detection in observations, respectively. The unfilled squares mark the species that are preferred by the models with and without PAHs. All the points with symbols except those with crosses indicate that the modeled abundances are within one order of magnitude of the observed ones.