SNIbc to SNII ratio as a function of host galaxy SN multiplicity. Top panel: the full sample. The bin for galaxies with  ≥ 4 SNe has a weighted mean number of SNe of 4.7. Error bars on the ratios are calculated using Poisson statistics (if the number of SNe within a distribution is less than 100, then we use Gehrels 1986 to estimate errors). The x-axis errors bars on the last point for  ≥ 4 SNe show the standard deviation on the mean number of SNe within each galaxy within the bin. Bottom panel: a sub-sample containing only SNe discovered after the year 1990 (see Sect. 4.2 for more discussion). Here the bin for galaxies with  ≥ 4 SNe has a weighted mean number of SNe of 5.