Galaxy cluster merger rate as a function of redshift normalised by the corresponding number of synthetic cluster regions in each mass bin (see Section 4.1) for major mergers with ∆M/M ≥ 0.5. Best-fit curves to simulated data are shown. Left panel: data points correspond to progenitor cluster masses with M_200,1 ≥ 10¹³ M_⊙ assuming Poissonian errors. Right panel: best-fit curves for progenitor cluster masses with 10¹³ ≤ M_200,ı/M_⊙ < 10¹⁴ (blue) and M₂₀₀,₁ ≥ 10¹⁴ M_⊙ (red). Data points are excluded for clarity. Solid and dashed lines indicate two different cuts of the merger ratio parameter, µ.