Sensitivity of the cross-calibration methods (as denoted in each panel) to activity levels during periods used to build the conversion relationships. Shown are the differences between the calibrated group counts for the synthetic data (cycle 16 was excluded from the calibration) and for the data where all cycles were considered for the calibration ($\mathrm{\Delta }G=G_A^{\prime \mathrm{SC}}-G_A^{\prime }$). The results for the different acuities are colour-coded as denoted at the top of the figure. The dashed lines denote that the criteria of that method would exclude this series from the calibration. To visualise the phase of the solar cycle, we also show a scaled version of the group counts from RGO, depicted as a shaded grey surface, while the part that is excluded from the cross-calibration is denoted in dark grey. Shown are the annual mean values. The numbers at the bottom of each panel denote the conventional solar cycle numbering.