Time evolution of the continuum properties of PKS 1830−211 during our monitoring in 2016 (see Table 1): (a) Flux density of the NE and SW images (error bars of 20% are indicated for the NE image data points only; the color code indicates the source used for flux density calibration). (b) NE/SW flux density ratio. (c) Difference in flux density between the XX and YY polarizers normalized by the Stokes I flux density. (d) Polarization ratio ℛ_pol (values are encoded as a function of the PA of the observations). (e) Difference in spectral index. The expected time delay of ∼27 days between the two lensed images of the quasar is indicated in panel a.