  Gravitational-wave detections are enabling measurements of the rate of
coalescences of binaries composed of two compact objects -- neutron stars
and/or black holes. The coalescence rate of binaries containing neutron stars
is further constrained by electromagnetic observations, including Galactic
radio binary pulsars and short gamma-ray bursts. Meanwhile, increasingly
sophisticated models of compact objects merging through a variety of
evolutionary channels produce a range of theoretically predicted rates. Rapid
improvements in instrument sensitivity, along with plans for new and improved
surveys, make this an opportune time to summarise the existing observational
and theoretical knowledge of compact-binary coalescence rates.
