Evolution of the unbiased SPT detection significance ζ at the pivot mass 3 × 10¹⁴ M_⊙/h₁₀₀ as a function of redshift. The red band indicates the main result of this work. The blue dashed curves indicate the corresponding 1σ band from the S21 analysis for comparison. The red and blue data points represent the corresponding binned analyses. They are placed in the centre of the bins. Horizontal error bars represent the bin widths. The redshift evolution parameter is fixed to C_SZ = 1.34 for our binned analysis. The diagonally hatched and vertically hatched bands correspond to the relations from the B19 study and the SPT cluster counts in combination with a flat PlanckνΛCDM cosmology, respectively. The displayed uncertainties correspond to the 68% credible interval (bands for the full relation and error bars for the binned analysis).