Temporal evolution of various dynamical state indicators based on the IGL, shown separately for each group class: (a) the total IGL mass; (b) the IGL mass fraction; (c) the m₁ plus total IGL mass fraction; and (d) the m₁ mass fraction. All luminous mass fractions are expressed relative to the invariant total stellar mass of the groups. Data points represent the mean values for each class, with the associated transparent shaded bands surrounding them indicating the standard error. The central vertical solid and dashed left and right lines in the panels mark, respectively, the Q₂, Q₁ and Q₃ quartiles of the distribution of turnaround times for the entire group sample. Group classes are colour-coded as in Fig. 3.