Posterior predicted trends with stellar mass, for galaxies of average size. Top: average projected mass enclosed within 5 kpc. Middle: average density slope. Bottom: average stellar velocity dispersion. Each band marks the 68% credible region. The magenta band shows the prediction for the parent population. The cyan band shows the prediction from the lens-only analysis, without accounting for selection effects. Dashed blue lines show the prediction for the population of SLACS lenses. Solid black lines show the prediction for the population of detectable lenses (obtained by removing the lens finding probability P_find from the posterior prediction). Error bars are the values measured for the SLACS lenses, assuming a flat prior on both m₅ and γ. Uncertainties on the stellar mass are uncorrelated with those on m₅, γ and σ_ap. In the bottom panel, the green line shows our quadratic fit to the m_* − σ_ap relation of the parent sample.