Fractional filament areas derived from the composite filament area series. We show annual median values of the disc-integrated areas (green) as well as polar filament fractional areas (multiplied by 10) for latitudes −90° to −50° (red) and 50° to 90° (blue). The shaded green surface denotes the asymmetric 1σ interval of the disc-integrated areas. We also show in black the ISN series. Its values are given on the right y-axis. The numbers within the panels denote the conventional solar cycle numbering.