Notably, ChemDiv is the compound data set with the largest number of compounds (27,543) meaning that the larger data set is not necessarily the one with the largest structural diversity, as clearly shown here. Similar results have been obtained for other data sets. These results further emphasize the need to quantify the structural diversity. Similar conclusions regarding the relative diversity of the compound libraries were obtained with other extended similarity indices (in addition to Tanimoto) and MACCS keys, as shown in Figure in the Supporting Information.