Charging up the $XYZ$ spectrum: recent experimental developments in charmonium spectroscopy

Over the last decade many new states, often dubbed $X$, $Y$, or $Z$, have been discovered in the excited charmonium spectrum. It has long been noted that several of these states have masses, widths, or decay modes that seem to be inconsistent with a simple quark-antiquark ($c\bar{c}$) interpretation. In the past year, the spectrum of $XYZ$ states has become broader with the discovery of multiple structures in the charmonium system that have electric charge, and therefore cannot be $c\bar{c}$ mesons. In this talk, I will review the recent developments in excited charmonium spectroscopy using data collected with the BESIII, Belle, and CLEO-c detectors. The results will be discussed in the context of both the known charmonium and bottomonium spectra, and prospects for future study will be presented.