We present some illustrative models of cosmic chemical evolution and compare them with the observed abundances of neutral hydrogen, heavy elements, and dust in damped Lymanα systems. To allow for a wide range of possibilities, we consider closed-box, inflow, and outflow models. The novel feature of our models is a self-consistent correction for the absorbers that are missing from existing samples as a result of the obscuration of background quasars. This is accomplished by assuming that the dust-to-gas ratio is proportional to the mean metallicity in the absorbers. Our models reproduce all of the available data on damped Lymanα systems, including the mean metallicity Z ≍ 0.1 Zsun at z ≍ 2.2, without any fine tuning of the input parameters. The models are also consistent with the average properties of present-day galaxies. The rapid rise in the mean metallicity with decreasing redshift is caused by high rates of star formation at 1 ≲ z ≲ 2. In contrast, models without obscuration have less star formation at these redshifts and fail to match the mean metallicity in the damped Lymanα systems.