Number density of pairs of quiescent galaxies at each snapshot. Blue circles, green triangles, and yellow inverse triangles correspond to those of the TNG300, SHARK, and GAEA, respectively. Their error bar is determined based on the Poisson noise. The red star shows the observationally estimated number density from the CEERS survey volume. Its error bar along the x-axis is ±0.5 Gyr, which is the time used in deriving the number density.