Cumulative fluence distribution for the subset of GRBs with a relative error on fluence below 20% (shaded histogram). The dashed histogram is the corresponding fluence distribution published by F09 for the entire GRBM catalogue of GRBs, as derived from 2-channel spectra. The solid line shows the power law distribution with index −3/2 expected if GRBs were homogeneously distributed in an Euclidean space throughout the sampled volume.