Deuteron-to-pion (top panel), and $^3$He-to-pion (bottom panel) yield ratios as a function of the charged-particle multiplicity density. All yields are measured at midrapidity, i.e., $\left|y\right|< $ 0.5 for pp, Xe$-$Xe and Pb$-$Pb collisions, and $-1< \left|y\right|< 0$ for p$-$Pb collisions. Lines represent statistical uncertainties, whereas boxes show systematic ones. The solid lines correspond to the expectations of two implementations of the CSM, see text for details.