Total multiplicity fraction of systems with q > 0.6 as a function of logarithmic age, colour-coded by the mean main-sequence mass of each open cluster. Top-left panel: for the 202 open clusters in our sample. The dashed blue line is the running median, and the errorbars are calculated as the 16th and 84th percentiles. Top-right panel: same for the 219 well-fit simulated open clusters. Bottom panels: same as above, but now split into four bins of mean-sequence mass, both for the observed Gaia OCs (left) and for the simulated clusters (right).