Values of $\frac{2}{\langle N_{\rm part} \rangle} \langle N_{\rm ch} \rangle$ for minimum-bias pp, p$\bar{\rm p}$, p$-$Pb and central AA collisions as a function of $\sqrt{s_{\rm NN}}$ are shown. The $s_{\mathrm{NN}}$-dependencies of INEL pp (p$\bar{\rm p}$) and NSD pp (p$\bar{\rm p}$) collisions are proportional to $s_{\mathrm{NN}}^{0.120}$ and $s_{\mathrm{NN}}^{0.127}$ respectively. The results from central AA collisions are proportional to $s_{\mathrm{NN}}^{0.192}$. The bands represent the uncertainties on the extracted power-law dependencies.