Morphology distributions of galaxy samples used in this work and the works with which we compare. The morphological types used for the AMIGA and HG84 samples are from the AMIGA database, while those for Solanes et al. (1996) are taken from the original article. The dark grey bars (detections) combined with the light grey bars (marginals and non-detections) make up the AMIGA HI science sample, which has a median type of 4 (Sbc). For comparison the white bars show the full CIG sample. The pink bars shown the field sample of Solanes et al. (1996), which has a median type of 6 (Scd), and the green bars the CIG-based sample of HG84, which has a median type of 5 (Sc).