a) Comparison of magnesium depletion for data available from the literature (denoted by different colours and symbols) and b) comparison of the magnesium depletion averaged for objects of each of four types LISM (local interstellar medium), H ii regions, our Mg ii sample (this paper), and DLA-QSO-GRB (damped Lyα absorption – quasi-stellar object – gamma-ray burst) absorption systems. [α/H] is [O/H] for LISM, H ii regions, and our sample galaxies, and [S/H] for DLA-QSA-GRB absorption systems.