for an approximate functional Ẽ[ρ], where ρ HF is the self-consistent HF density and ρ LDA is the self-consistent density computed using the local density approximation (LDA). Burke and co-workers suggest S > 2 kcal/mol as an indicator of cases that are likely to be dominated by density-driven error (or S > 8 kJ/mol in the units that will be used herein), although that threshold was calibrated using small molecules. For larger systems with unpaired spins, one can find examples where S ranges from 150-650 kJ/mol across a set of similar chemical systems. This suggests using