Bottom panel: per cent difference between the values estimated in redshift space and in real space using spherical cells with a radius of 4 h^-1 Mpc as a function of 1 + δ_MAX (see Eq. (7)). The different curves refer to different redshift shells and magnitude cuts, as indicated in the plot. Upper panel: per cent difference in the estimated non-linear parameter . Vertical dashed lines are drawn in correspondence to the δ_MAX values at which systematic errors are computed and listed in Table 2.