Influence of scatter on the GSMF. Shown are the modelled stellar mass functions for a fixed set of model parameters at z = 0. The grey line shows the GSMF calculated assuming a one-to-one relationship between the quantities and halo masses, as done throughout this paper. The pink lines show the GSMF calculated using the same parameter but adding a Gaussian scatter to the stellar mass – halo mass relation with different variances. The high-mass slope is strongly sensitive to the amount of scatter, while the normalisation is weakly affected and the low-mass slope unaffected.