GFN-xTB and DFTB-D3 are the most accurate semi-empirical methods with MUEs of 3.9 and 3.7 kcal/mol, followed by DFTB (4.5 kcal/mol) and PM3 (4.8 kcal/mol) -with both pairs of methods being statistically identical (Table ). The good performance of GFN-xTB and DFTB-D3 is especially remarkable because they are not specifically parameterized against any reaction energies. Comparison of the MUEs for DFTB-D3 and DFTB shows that dispersion corrections lead to noticeably more accurate reaction enthalpies for DFTB, consistent with previous findings. The remaining NDDO-based methods have statistically identical accuracy, with MUEs in the range 5.2 to 5.9 kcal/mol, with the exception of PM6-D3H+, which has en MUE of 6.5 kcal/mol. The MUEs for PM6, PM6-DH+, PM6-D3, PM6-D3H4X, and PM7 are computed without reaction 23, which is a clear outlier and will be discussed in detail in the next subsection. Furthermore, Reactions 16 and 22 are omitted for OM2 because it is not parameterised for fluorine. We note that PM6-D3H+ has an Dev-2 error of 15.0 kcal/mol and is therefore not considered an outlier. So while the MUE for PM6-D3H+ is higher than for the other PM6-based methods it does not lead to any outliers using the Dev-2 method. For the semi-empirical methods there is little correlation between the MUE for parent reaction and the CBH-2-corrected values. Similarly, with an MUE of 6.8 kcal/mol OM2 performs reasonably well for the parent reactions, but worst with CBH-2.