  Type IIn supernovae potentially constitute a large fraction of the
gravitationally lensed supernovae predicted to be found with upcoming
facilities. However, the local rate is used for these estimates, which is
assumed to be independent of properties such as the host galaxy mass. Some
studies hint that a host galaxy mass bias may exist for IIn supernovae. This
paper aims to provide an updated local IIn supernova-to-core-collapse ratio
based on data from the Palomar Transient Factory (PTF) and the Zwicky Transient
Facility (ZTF) Bright Transient Survey (BTS). Furthermore, the goal is to
investigate the dependency of the IIn supernova peak magnitude on the host
galaxy mass and the consequences of a possible host galaxy mass preference on
the volumetric rate of type IIn supernovae. We constructed approximately
volume-limited subsamples to determine the local IIn supernova-to-core-collapse
ratio. We investigated the absolute peak magnitude of a subsample of type IIn
and superluminous II or IIn supernovae exploring how this relates to the i-band
magnitude of the host galaxies (as a proxy for stellar mass). We presented a
method to quantify the effect of a potential preference for low-mass host
galaxies utilizing the UniverseMachine algorithm. The IIn
supernova-to-core-collapse ratios for PTF and BTS are 0.046 +- 0.013 and 0.048
+- 0.011, respectively, which results in a ratio of 0.047 +- 0.009, which is
consistent with the ratio of 0.05 currently used to estimate the number of
gravitationally lensed IIn supernovae. We report fainter host galaxy median
absolute magnitudes for type IIn brighter than -20.5 mag with a 3 sigma
significance. If the IIn supernova-to-core-collapse ratio were described by the
power law model $IIn/CC = 0.15 \cdot \log(M/M_{\odot})^{-0.05}$, we would
expect a slightly elevated volumetric rate for redshifts beyond 3.2.
