Ratio ${r_X}$ of the charged-particle pseudorapidity density in Pb$-$Pb (top) and p$-$Pb (bottom) in different centrality classes to the charged-particle pseudorapidity density in pp in the INEL$>0$ event class. Note, for Pb$-$Pb $\eta_{\rm lab}$ is the same as the centre-of-mass pseudorapidity.