be inferred.

The number of imitation HI masses per decade of $M_{HI}$ becomes $$\hat\phi_{im}\approx 2.3{\times}10^{-5}
   \left(\frac{M_{HI}}{M_{HI}^*}\right)^{-1.15}
   \left(\frac{z}{z_{OH}}\right)^{0.3} {\rm Mpc}^{-3}$$ This estimate implies that a survey sensitive to 1 mJy signals, corresponding to $M_{HI}$ between $10^5$ and $10^6$M$_{\odot}$ at velocities of 300 to 500 km s$^{-1}$, would be unlikely to detect more than one imitator per cubic megaparsec. Therefore, with the current set of parameters describing the OH luminosity function, significant contamination of HI surveys at low redshift would only occur if the HI mass function turns out to be as flat as $\gamma\approx 1$ or drops off at low $M_{HI}$. Even substantial evolution in the merging rate from $z=0$ to 0.17 is unlikely to raise this density estimate by more than a factor of two, but some caution is in order until our understanding of the properties of OH masers improves. The likelihood for confusion might rise significantly if surveys were conducted at a 0.2 mJy sensitivity.

Conclusion
==========

The density of OH megamaser galaxies in the sky may be high enough that radio spectroscopic surveys will be effective tools at identifying them. The time evolution of the megamaser sources could then be monitored by a series of surveys performed 