  We present the current results of a survey for OH megamasers (OHMs) underway
at the Arecibo Observatory. The survey is 2/3 complete and has produced a high
OHM detection rate (1 in 6) from a redshift-selected sample of IRAS galaxies.
The survey will relate the OHM luminosity function to the galaxy merger rate,
allowing subsequent blind OHM surveys to measure the galaxy merger rate as a
function of cosmic time. The survey has also made the first detection of strong
variability in OHMs. Variability will provide a powerful tool for understanding
the small-scale physical settings and mechanisms of OHMs.
