Left and middle panels: predicted M_•-M_Bulgeprobability distributions for the samples of Merloni et al. (2010) (blue filled circles) and Jahnke et al. (2009) (yellow squares), using our model 1 (left) and model 2 (middle) assumptions about the distribution functions. In each panel, the black solid line shows  ⟨ μ ⟩ (s), the red dashed-dotted line shows  ⟨ s ⟩ (μ), and the thin black dashed line delineates the reference z ≈ 0 relation. Right panel: redshift dependence of the observed M_• /M_Bulge  ratios, expressed as offset Δμ from the z = 0 relation, together with the predicted evolution of the sample bias. The symbols are as before, plus the large open circles that show the mean offset for the Merloni data in three redshift bins, and the large open square showing the mean of the Jahnke data. The dashed line shows our prediction for model 1, the solid line with the shaded area shows our prediction for model 2, including the uncertainties on the spheroid mass function. The dashed-dotted line is for model 1, but assuming evolution in the M_•-M_Bulgerelation M_•/M_Bulge ∝ (1 + z).