Detection probability of Mg II absorbers. Left panel: Detection fraction as a function of redshift. The average DECaLS r_mag of galaxies per redshift bin is shown as a square, along with the 16th and 84th percentiles. Right panel: Equivalent width (W₂₇₉₆) distribution of Mg II absorbers for entire sample with z < 1 (solid histogram). The hatched histogram shows the distribution for the detection set, given in the right-hand-side ordinates. The detection fraction per W₂₇₉₆ bin is shown as a square symbol given in the additional y axis, the right-hand-side ordinates.