Extended S_MWO time series. The green point originates from the Wright et al. (2004) catalogue, the black points are from the Isaacson & Fischer (2010) catalogue, the blue points are TIGRE S_MWO values, and the red diamonds represent the observational seasonal mean S_MWO values. The dashed lines depict a sine fit with a period of 12 yr (dashed red line) and 15 yr (dashed black line). The solid lines depict double sine fits (the colour-code is the same as for the single sine fits), where the short-term cycle period of 2.6 yr is also considered.