Cluster mass vs. shell mass for the three stellar association scales and the CO dynamically derived values. The label in the upper left corner shows which values the subplot represents. The marker colour shows the age for each method and the marker sizes indicate the bubble radius. The dashed black line indicates the values that correspond to a SFE = 1%. For each method, also plotted is the residual each marker is away from equalling a SFE of 1% directly underneath as a new subplot.