Figure 5: Median, mean, and of fractional polarization for flat- (a) and steep-spectrum (b) sources. Black points refer to the almost complete subsample of the AT20G survey with mJy for flat-spectrum sources and 300 mJy for steep-spectrum sources. Red points refer to data presented in . Green points refer to the B3-VLA sample (with respect to , we distinguish flat- and steep-sources on the basis of their spectral index between 1.4 and 5 GHz; values shown in the plot are obtained using the ASURV code, taking into account upper limits in the fractional polarization). Cyan points refer to the sample from  (see text and Table 2; empty cyan points at 43 GHz for the steep-spectrum have to be considered as upper limits). Blue points refer to results from  and magenta points from  (solid and empty points are for FSRQs and BL Lacs, resp.). Yellow points refer to the NVSS survey (see ): for steep-spectrum sources we plot results for sources with mJy and mJy.