  The centrality dependence of midrapidity charged-particle multiplicities at a
nucleon-nucleon center-of-mass energy of 2.76 TeV from CMS are compared to
PHOBOS data at 200 and 19.6 GeV. The results are first fitted with a
two-component model which parameterizes the separate contributions of nucleon
participants and nucleon-nucleon collisions. A more direct comparison involves
ratios of multiplicity densities per participant pair between the different
collision energies. The results support and extend earlier indications that the
influences of centrality and collision energy on midrapidity charged-particle
multiplicities are to a large degree independent.
