Redshift dependence of ${\overline{q}}_{\mathrm{IR}}$. The “q_IR mean”, “q_IR mean corr”, and “q_IR mean SB” lines refer, respectively, to the initial Delhaize/MIGHTEE sample, the same sample but with S​_1.4 GHz flux densities and upper limits derived from the 3 GHz survey scaled up by a factor of 1.51, and to this latter sample after removing SMGs with SFR < 10 M_⊙ yr⁻¹ (“starburst plus protospheroid” sample). Error bars are omitted so as to avoid overcrowding. The “Delhaize fit” line shows the power-law fit, ${\overline{q}}_{\mathrm{IR}}(z)=2.88{(1+z)}^{-0.19}$, obtained by Delhaize et al. (2017). The results of our analysis of the Negrello et al. (2017) sample and of the study of Algera et al. (2020) are also shown.