Distribution of the number density of strong Mg ii absorbers per comoving Mpc with respect to the absorbers’ wavelength in the quasar rest-frame, λ_sup = λ_obs/(1 + z_em). We fit two power laws to the distribution: one is fitted to the number densities at continuum dominated wavelength bins only (violet curve), while the other is fitted to the entire dataset (blue curve). Error bars are Poissonian. Vertical lines indicate the wavelengths of the quasar broad emission lines C iv λ 1550, C iii]  λ 1909, and Mg ii λ 2800. The peak at Mg ii (i.e., z_abs ≈ z_em) is expected, as some quasars display intrinsic Mg ii absorption.