And Don't Forget The Black Holes
  The discovery of the highly relativistic neutron star (NS) binary (in which both NS's are pulsars) not only increases the estimated merging rate for the two NS's by a large factor, but also adds the missing link in the double helium star model of binary NS evolution. This model gives $\sim 20$ times more gravitational merging of low-mass black-hole (LMBH), NS binaries than binary NS's, whatever the rate for the latter is. 
H.A. Bethe, G.E. Brown, C.-H. Lee