Joint probability distributions of density fields of dark matter and galaxies with different formation epochs on the scale of ﹩R_{s}=8\,h^{-1}﹩ Mpc. Left panel: galaxies with ﹩z_{f}> 1.7﹩; right panel: galaxies with ﹩z_{f}< 1.7﹩. Solid lines: Simulated mean relations. For comparison, the predictions of mean biasing for dark halos with formation redshift greater and less than 1.7 are shown in left and right panels, respectively.