Radial component of the relative cluster motions (v_r) versus the tangential component (v_tan) (left panel), and versus formation time (right panel), with e Lup as a reference point. Symbols and colours are as in Fig. 4. The dashed grey line in the left panel is a 1-to-1 line. The dashed dark grey line in the right panel shows a linear fit to data of 23 clusters, after removing the seven red-circled and the two dashed black-circled clusters. The solid light grey line at v_r = 0 in both panels marks the transition from radial outward motion (> 0) to inward motion (< 0).