Two-dimensional χ_eff – mass ratio q histograms of the BH–BH merger rates density $\frac{{\mathrm{dR}}_{\mathrm{BHBH}}}{\mathrm{dq}\mathrm{d}{\chi }_{\mathrm{eff}}}$ [Gpc⁻³ yr⁻¹] at redshift z < 1.0. This figure only shows the systems formed via the SMT subchannel (CE subchannel not included). We present the results for two natal kick variants. In the left panel is a model with fallback-decreased natal kicks (default), and in the right panel is a model with non-fallback decreased magnitudes (full kick).