Cumulative number density of overdense regions of g-dropout galaxies (left) and dark matter halos (right). In the right-hand panel, the solid lines represent halo mass functions at z ∼ 3.8 with different cosmology (black: WMAP9; blue: Planck), and the halo mass function at z = 0 is shown by the dashed line. The horizontal line (red) indicates the number density of protocluster candidates at z ∼ 3.8 (>4 σ overdense regions). It should be noted that the number density of descendant clusters at z = 0 would be smaller than that of protoclusters at z ∼ 3.8 due to merging.