The assumption made by the standard correction method, that the DFT reference states are off by a shift, is a valid hypothesis, but if it were the correct hypothesis, the standard method would correct the non-1 slope. This is not what is seen when we consider oxides, where the standard correction has a large effect: In figure ; the non-1 slope in 1D is not corrected in 1E. This presents evidence that the hypothesis that only additive errors are present in DFT is either incorrect or insufficient.