  We show that the dependence of the charged particle multiplicity on the
centre-of-mass energy of the collision is, in the String Percolation Model,
driven by the same power law behavior in both proton-proton and nucleus-
nucleus collisions. The observed different growths are a result of energy-
momentum constraints that limit the number of formed strings at low en- ergy.
Based on the very good description of the existing data, we provide predictions
for future high energy LHC runs.
