Top panel: histogram for the decline rates between 0 and 50 d after peak brightness for 27 of our SNe IIn. A single Gaussian (identified using GMM with BIC) describing the whole population is shown in blue, but our SNe IIn might possibly divide into fast (grey dash-dot lines) and slow (grey dotted lines) decliners, with slopes 0.040 ± 0.010 mag d⁻¹ and 0.013 ± 0.006 mag d⁻¹, respectively (suggested by GMM with AIC). The respective mean decline rates are shown as solid grey lines. Central panel: two possible clusters of SNe IIn (slow and fast decliners) compared to the prototypical slow and fast decliners from the literature (SN 1988Z, Aretxaga et al. 1999; SN 1998S, Liu et al. 2000). Bottom panel: light-curves of the N(SNe) = 27 of our SNe IIn with measured decline rates (between 0 and 50 d), scaled to match at peak. The two different decline rates are overplotted. Fast (grey dash-dot lines) and slow (grey dotted lines) decliners are shown, with the respective mean decline rates marked with solid grey lines.