Star formation efficiency versus halo circular velocity and mass at two different epochs in our toy model (Eq. (8)). This figure has been plotted for the parameters of Table 1 that produce the best fit to the stellar mass function at z = 0 (see Sect. 3.1). The upper (black) mass scale is for z = 0, while the lower (red) mass scale is for z = 5. The gold shaded region shows the relation predicted by abundance matching by Guo et al. (2010).