Median q_IR as a function of redshift obtained by analysing the SFG sample of Delhaize et al. (2017, stars). Black lines indicate the median q_IR − z trend of Delhaize et al. (2017) before (dot-dashed) and after (triple dot-dashed) removing 2σ outliers. The grey solid line marks the resulting best-fit q_IR trend with redshift, that is highly consistent with that of Delhaize et al. (2017) after removing radio AGN. Numbers below each star denote the median M_⋆ of the underlying sample.