Total mass (M₂₀₀) versus redshift of the group and cluster samples. The low mass (poor) groups (6 × 10¹² < M₂₀₀ < 6 × 10¹³ M_⊙) are identified by the green symbols. The high mass (rich) groups (6 × 10¹³ < M₂₀₀ < 2 × 10¹⁴ M_⊙) are identified by the magenta symbols. Black symbols show the sample of clusters, all with M₂₀₀ > 2 × 10¹⁴ M_⊙. The stacked groups of Guo et al. (2014) are shown with a empty circles. The stacked clusters of Haines et al. (2013) are shown with filled squares. The high redshift group of Smail et al. (2014) is shown with a filled point. Green stars and filled magenta triangles show the low mass and high mass groups of Popesso et al. (2015), respectively. Filled black triangles show the cluster sample of Popesso et al. (2012) with the addition of the Coma cluster of Bai et al. (2006). The typical error of M₂₀₀ for the low and high mass group samples is on the order of 0.2 dex, so much smaller than the M₂₀₀ bin size considered in this analysis. The typical error of the bright clusters is on the order of 10% in the totality of the cases.