Both top-down and bottom-up screening can achieve good fidelity with respect to the corresponding supersystem calculation at the same level of theory. topdown fragmentation has a significant drawback in that it requires a well-defined screening protocol for each n-body order, and lower orders in the expansion do not benefit directly from the screening performed at higher orders, when it comes to constructing the graph of non-negligible subsystem nodes. Even for a screening protocol as simple as Eq. ( ), where n-body terms are excluded based on an energy threshold τ n , the top-down approach is impractical for large systems when n > 3, because every high-order n-body subsystem must be considered individually.