Left-hand panel: the unbinned data points for all potential components in our sample, plotted as a density histogram. We plot the fraction of the total 250-μm source flux assigned to each potential component, as a function of the total 250-μm flux. Colour indicates the log of the number of points contained within that bin, as indicated by the colour bar on the far right. Points close to 1 on the y-axis indicate that they were assigned almost 100 per cent of the total flux, meaning that they are the only source assigned significant flux. For high total flux 250-μm sources, there is a deficit of components at large flux fractions (i.e. high-flux objects tend to have that flux divided amongst more components, explored in more detail in text). The right-hand panel shows a histogram of the distribution of flux fractions across all 250-μm source fluxes. The x-axis in the right-hand panel is in log space.