Histograms of halo masses for three comoving boxes located at z = 0 (top panel), z = 1 (central panel), and z = 3 (bottom panel). In all panels, we show the distribution of observed mass (violet) and infall mass (brown) of subhalos that have entered R₂₀₀ of their main halo (i.e., are located at R <  R_{200, main halo}). We also show the distribution of observed (red) and infall (blue) masses of all subhalos and the mass distribution of main (or central) halos with subhalos (light blue), the distribution of main halos without subhalos (orange), the total distribution of all main halos (green), and the distribution of all halos (black; i.e., both main and subhalos) considering the infall mass for subhalos.