Stellar mass fraction, f_mass, of each population in the stellar halo: in-situ (blue area), endo-debris (light green area), and ex-situ (orange area) stars as a function of the galactocentric radius in units of its corresponding virial radius, r_vir. Stellar halos are sorted by decreasing their stellar galaxy mass, M_⋆, gal. The vertical line depicts the 1.5r_opt in units of r_vir. The dashed, horizontal line indicates f_mass = 0.5.