Halo mass dependence of the fraction of groups with ΔM_1,2> 1. Black points with error bars show the data and dotted red, dashed blue and dash-dotted green histograms present model predictions of G11, B06 and DLB07, respectively for S–I (top left panel), S–II (top right panel), S–III (bottom left panel) and S–IV (bottom right panel). While the data are in agreement with the models, the low statistics of the data prevents us from choosing the best model.