Sky distribution of 283 GRBs with redshift in Galactic coordinates (blue squares), overlaid by modelled angular biases. The Galactic equator region (lightly mottled) is under-sampled because of Galactic extinction effects on redshift measurements. The ecliptic polar regions (pink mottled) are oversampled relative to ecliptic equator regions because of Swift’s sky exposure. The anisotropic distribution of the 31 GRBs at 1.6 ≤ z ≤ 2.1 (red crosses) is largely unaffected by these biases; sampling biases have not favoured their detection.