Difference of the proper motion in RA (top panels) and Dec (bottom panels) by van Leeuwen et al. (2000) and Gaia Collaboration (2018b) as a function of magnitude (left panels) and of colour (right panels). Stars are coloured as in the previous figures. The average difference between the two catalogues are plotted as grey dotted lines, the ones for each sub-population are plotted as dotted lines of the respective colours, and the linear fits for each sub-population are shown as solid lines of the respective colours. None of the slopes are statistically significant, even the few that appear large are driven by single data points and a small sample size (see Sect. 2 and Table 2).