z–E distribution for the selected CHIME/FRB Catalog 2 sample. The black points show the catalog events, with the colorbar indicating the marginal fluence-only projection of the selection function. The red solid line represents the fluence-limited selection boundary at F_ν,th = 5 Jy ms, which is used to define the comparable sets in the weighted Lynden-Bell C⁻ method. The pink point (z_i, E_i) is used to illustrate the definition of the comparable sets ﹩{J}_{{z}_{i}}﹩ and ﹩{J}_{{E}_{i}}﹩, which are defined by the green and purple dashed lines, respectively.