Top: smoothed monthly mean ISN (black) and HSN (north: blue, south: red) from the merged data set for the time range 1874–2020. The shading of the difference between the north and south sunspot numbers indicates the excess between them. Dashed vertical lines are drawn at sunspot minima to delineate the individual cycles. Bottom: cumulative monthly mean HSN calculated individually for each of the cycles 12–24.