The generally poor correlation between the charges obtained with different schemes raises some questions about the different roles and interpretations partial charges can have. On one hand, they can reflect a local partitioning of the electron density, as in the case of Mulliken, Hirshfeld or Bader charges. On the other hand, they can reflect the electrostatic potential on the surface of a molecules, as in the case of ChelpG and related schemes. While the latter is arguably less arbitrary (as it is directly tied to a physical observable) it has well-known issues with assigning meaningful charges to atoms that are "buried" in bulky molecules.