  We compare the luminosity function and rate inferred from the BATSE short
hard bursts (SHBs) peak flux distribution with the redshift and luminosity
distributions of SHBs observed by Swift/HETE II. While the Swift/HETE II SHB
sample is incompatible with SHB population that follows the star formation
rate, it is compatible with a SHB rate that reflect a distribution of delay
times after the SFR. This would be the case if SHBs are associated with binary
neutron star mergers. The available data allows, however, different
interpretations. For example, a population whose rate is independent of the
redshift fits the data very well. The implied SHB rates that we find range from
$\sim 8$ to $\sim 30h_{70}^3$Gpc$^{-3}$yr$^{-1}$. This is a much higher rate
than what was previously estimated. A detailed (2 dimensional) look at the best
fit models shows, however, some discrepancy between the four Swift/HETE II SHBs
and the models based on BATSE SHBs. This could be a statistical fluke. It could
also arise from wrong estimates of the triggering criteria or from selection
effects. If real it may indicate the existence of two SHB populations with
different luminosity functions and redshift distributions.
