Impact of prior-volume weights on the (pre-SOM) N(z) of the full spectroscopic compilation (upper panel), and on those galaxies in the compilation that end up in tomographic bin three both prior to the SOM re-weighting (middle panel) and after the SOM re-weighting (bottom panel). The systematic effect that the prior weight imparts on the tomographic bin is particularly clear prior to re-weighting by the SOM to match the wide-field sample but is somewhat diluted by the SOM re-weighting process. Nonetheless, there is a residual difference after the SOM re-weighting in the bottom panel. This difference is exacerbated if one does not have high quality image simulations to calibrate the underlying N(z) bias (dashed lines in the bottom figure; discussed further in Sect. 6), as the non-prior weighted N(z) estimate contains a significant systematic bias (⟨δz⟩≈0.03), whereas the prior weighted N(z) estimate has no bias (⟨δz⟩≈0.004).