The modulation index change, Δm_i, as a source passes from the farthest to the closest point to the Sun plotted versus ecliptic latitude β. The two-degree (black dots) and five-degree average (orange dots) pinpoint the large increase in variability for sources with low β. The variation deduced from Urumqi observation for AO 0235+164, plotted as a cyan square, has been obtained excluding the April 2007 and April 2008 observations, and should be regarded as a lower limit.