  We have calculated the detectable merger rate of primordial black holes, as a
function of the redshift, as well as the binary's mass ratio, total mass and
chirp mass (observables that have not previously been explored in great detail
for PBHs). We consider both the current and design sensitivity of LIGO and five
different primordial black hole mass functions, as well as showing a comparison
to a predicted astrophysical black hole merger rate. We show that the empirical
preference for nearly equal-mass binaries in current LIGO/Virgo data can be
consistent with a PBH hypothesis once observational selection effects are taken
into account. However, current data do exclude some PBH mass distributions, and
future data may be able to rule out the possibility that all observed BH
mergers had a primordial origin.
