Relation between the wing strength (the cumulative sum of the monthly numbers of sunspot groups) and the H, F, and L latitudes in panels a) to c), respectively, separately for the two datasets (RGO and Schwabe) and the two hemispheres, as denoted in the legend of panel a). The blue and red dotted lines depict the best-fit linear trends for the N and S hemispheres, respectively, using the RGO data.