The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has made measurements of event-by-event fluctuations in the charged-particle multiplicity as a function of collision energy, centrality, collision species, and transverse momentum in several heavy-ion collision systems. It is observed that the fluctuations in terms of sigma(2)/mu(2) exhibit a universal power law scaling as a function of N-participants that is independent of the transverse momentum range of the measurement.