PDF of the fractional polarisation of the GN sources. The distribution of all detected sources in our sample are shown in blue (we note that the sources with FP ≤ 1% are excluded from all analysis since those values are very uncertain and probably heavily influenced by polarisation bias and leakage), while the orange sample (FP ≥ 1% and TP ≥ 10 mJy) is the sample used for fitting.