Radial-velocity fluctuations among different line groups, as a function of absorption-line depth. Standard deviations and jittering ranges in the simulation of integrated sunlight are shown, with numbers from the small simulation area (for the actual Sun, divide by a factor of ∼150−200). Stronger and deeper lines display greater amplitudes. The trends extend to the even stronger Na I D₁ line which, at 136 and 404 m s⁻¹, is off scale and not included for the fitting of the lines.