Posterior density of the normalised excess variance V(m) = [⟨N(N − 1)|m⟩−⟨N|m⟩²] ⟨N|m⟩⁻¹ (y-axis) as a function of halo mass m/h⁻¹ M_⊙ (x-axis) for the low-z galaxy samples (top) and high-z samples (bottom). The shaded regions are the 68% CIs around the median (black solid lines). The green lines show V(m) for H15 (solid) and L12 (dashed) directly from the ⟨N(N − 1)|m⟩ in the simulation snapshots.