Extrapolation to the total number of produced charged particles as a function of the number of participating nucleons. The light-gray band represents the uncorrelated errors from the extrapolation fit while the dark-gray band shows the increase to the total systematic errors which includes the common error coming from the uncertainty in the centrality estimation. The lower energy data from PHOBOS was scaled by the average number of charged particles per participant with $\Npart>180$ found in the ALICE measurements divided by the same quantity found in the PHOBOS measurements.