Proper motion measurements in right ascension (left panel) and declination (right panel). Gaia proper motions from Early Data Release 3 (EDR3, Gaia Collaboration 2021) are plotted against ground-based measurements from SDSS DR9 (Ahn et al. 2012, open circles), the PPMXL catalogue of positions and proper motions on the ICRS (Roeser et al. 2010, open squares), the Whole-Sky USNO-B1.0 Catalogue (Monet et al. 2003, open diamonds), the Absolute Proper motions Outside the Plane catalogue (APOP, Qi et al. 2015, open downward triangles), Gaia-PS1-SDSS (GPS1, Tian et al. 2017, open upward triangles), and Hot Stuff for One Year (HSOY, Altmann et al. 2017, crosses). PMs from the Fourth U.S. Naval Observatory CCD Astrograph Catalogue (UCAC4, Zacharias et al. 2013) were also used, but they are not plotted here, because only a few stars have measurements in this catalogue. The averages of the ground-based values from those surveys are plotted as filled diamonds. The ground-based measurements by Tillich et al. (2011) and Ziegerer et al. (2017) are plotted as open dark grey diamonds.