Latitudinal cuts through the butterfly diagram shown in Fig. 1 for the years 1903 (during the weak cycle 14, solid red curve) and 1957 (during the strong cycle 19, solid black curve). In the left panel, the dashed (dash-dotted) curve represents a Gaussian fit to the number of spot groups in the southern (northern) hemisphere. In the right panel, the two hemispheres were fitted together with a single Gaussian.