Maximum (orange lines) as well as dust-mass-weighted average (blue lines) and standard deviation (blue-shaded areas) of dust-to-gas volume density ratio ρ_d/ρ_g as a function of time after the dust particle initialisation t – t_d,init The maximum, mean, and standard deviation are well-correlated, with the Pearson correlation coefficients⁶ of maximum and mean being given in the top right of the panels. Three phases in the evolution of the volume density ratio in the SIwhileVSI simulation can be distinguished: an initial phase of sedimentation, followed by a quasi-steady phase, and a phase of strong clumping characterised by strong variations. In comparison, the simulation of the streaming instability never evolves into the strong-clumping phase, while the SIafterVSI simulation skips the quasi-steady phase.