We calculate the unseen-but-true GRB-event rate from a current flux-limited sample of 33 GRBs with individually measured redshifts .
We consider a GRB-event rate which is proportional to the star-formation rate , in view of the GRB-SNe association in SN1998bw and GRB030329 .
By fitting a log-normal distribution of GRB peak-luminosities , we find a ratio 1 / f _ { r } \simeq 450 
for the true-to-observed GRB-event rates .
This provides an independent derivation of the GRB-beaming factor 1 / f _ { b } \simeq 500 obtained by Frail et al .
( 2001 ) from sources with standard GRB-energies .
We discuss applications to GRB980425 .