Ratio of the X–S band core position shift measured at 2002 by Kovalev et al. (2008a) to the one measured in 2007 (this paper) as a function of the X band core flux density ratio at these two epochs. The core shift ratio is defined to be greater than unity, i.e., for each pair of measurements, the higher value of the shift is in the numerator of the ratio. The one source (not shown in this plot), which exhibited a large core shift change without a major change in flux density is W Com (1219 + 285); it has a core shift ratio of 3.67 ± 0.36 and core flux ratio of 1.19 ± 0.08.