Results for conjugated polymers allude to systemic problems with the description of long-range CT in TD-DFT calculations. These will be considered further in Section 6, and will ultimately require one or more metrics that can quantify the extent of CT character in a given excited state, to use as a diagnostic for when problems should be anticipated. A variety of CT metrics have been proposed and several of them are closely related to statistical measures of electron-hole separation that were introduced in Section 5.2, although these connections have seldom been made clear in the literature. For that reason, we introduce a few of these metrics here, in order to illustrate how they are connected to the physically-meaningful metrics introduced above.