Cluster formation efficiency as a function of star formation rate surface density. Colored points show individual outputs, while the colored error bars show the standard deviation around the mean of all points for a given simulation. Red crosses show estimates from observed galaxies considering young (1–10 Myr old) star clusters. Observed data shown are compiled by Cook et al. (2023) and include estimates from Goddard et al. (2010), Adamo et al. (2011, 2015, 2020a), Annibali et al. (2011), Pasquali et al. (2011), Cook et al. (2012), Lim & Lee (2015), Hollyhead et al. (2016), Chandar et al. (2017), Messa et al. (2018).