Combined 2 GHz variability curve of all the NESMP data. For each source, the flux densities have been de-trended and normalised according their standard deviation σ. Afterwards, the data of all the sources were stacked into a single light curve, which has been averaged over time bins of 0.01 yr. A one-year periodic ripple, resulting from the combination of the annual oscillations in the light curves, has been removed from the stacked data. The regular sequence of dips, with an average separation of 0.5 yr, is indicated with orange arrows, while a magenta arrow is reserved for the 1993.5 ESE.