The ratio of total H i and stellar masses, M_{H I}/M_⋆, as a function of total stellar mass, M_⋆ (in M_⊙). Black dots represent clear NIBLES detections, gray dots marginal detections, and red open triangles estimated upper limits for non-detections, whereas green dots represent the clear ALFALFA detections from Haynes et al. (2011). All total stellar masses used for the NIBLES and ALFALFA galaxies were taken from the SDSS “added-value” MPA/JHU catalogs (see Sect. 4). The H i masses of the ALFALFA detections were calculated in the same way as for the NIBLES sources, using simply a distance of D = V/H₀, where the adopted Hubble constant is H₀ = 70 km s^-1 Mpc^-1. The green vertical arrow on the right indicates the mean flux scale difference of 0.16 dex in log (M_{H I}) between the higher ALFALFA α.40 catalog H i line fluxes and the NIBLES values (see Sect. 4.6). For all fits made to the NIBLES data, we excluded sources that are either resolved, confused or missing significant SDSS flux. The dark green line shows a linear regression fit made only to the NIBLES detections. The dark blue line shows a linear regression fit to all NIBLES data including our rather conservative estimates for H i mass upper limits based on the upper envelope in the W₂₀–L_r relationship (Fig. 5), whereas the light blue line shows a fit using low upper limit estimates based on the mean W₂₀–L_r relationship (see text). The pink line shows the mean relationship derived for four literature reference samples of H i-detected local galaxies from Papastergis et al. (2012), which is based on a stellar mass estimation method different from the one used in the MPA/JHU catalogs (see Sect. 5.1). For the NIBLES detections, we indicate the typical uncertainty in both quantities by the black cross on the right hand side of the plot (see text for details).