FoMs obtained from the 1σ error ellipses of each pair of parameters of the scaling relation, taken from the different observables μ_j defined in Eq. (8). By FoM we denote the figure of merit computed as the volume of the 3-dimensional 68% error ellipsoid. To facilitate the understanding of this figure, the dark gray, gray and light gray areas denote observables accounting for the amplitude, the shape and the full shape of power spectra respectively. Results are shown in real space. Noticeably, the luminosity power spectrum P_L provides more information regarding the scaling relation than the luminosity-weighted spectra, and display a total FoM that is ~10² times that of the unweighted power spectrum. We show the estimates derived from the luminosity power spectrum , in order to emphasize how high FoM can be obtained when no shot-noise correction is spuriously implemented in the measurements.