C i λ1560 rest-frame equivalent width versus N(H i), the neutral atomic-hydrogen column density of C i absorbers. Intervening (resp. proximate) systems are displayed as filled (resp. empty) black circles. Data points are circled in red as they correspond to the subsample of C i systems with measured N(H i), i.e., the H i subsample. The dashed (resp. dashed-dotted) curve materializes the limit above which systems are expected to have a metallicity larger than one-tenth of solar (resp. in excess of solar; see text). The completeness limit of the survey is indicated by the horizontal line.