Observed and predicted redshift evolution of the offset in black hole masses for a sample of SDSS quasars. The green circles show the data from Salviander et al. (2007), using the [O iii] line width as surrogate of σ _∗ , the blue squares show their results using [O ii], and the yellow triangles show the results from Shen et al. (2008). The dashed and solid lines shows our model 1 and model 2, respectively, assuming no intrinsic evolution in the M_•-σ _∗ relation. The dashed-dotted and dotted lines give the predicted sample offsets for an evolution with γ = 1 for the two models. The shaded areas again incorporate the uncertainty on the spheroid mass function.