Please do not adjust margins Please do not adjust margins nanoporous materials, which is a prohibitively large candidate pool and includes families of materials that as yet have produced no confirmed electrides, such as metal-organicframeworks or MOFs. Thus, the feature of void space within the crystal structure remains intractable as an early approach to high-throughput analysis for the time being. The heuristic rule of strongly electron-donating constituent elements is one feature to which all confirmed electrides conform and one that could in theory be the starting point for an electride search. At the time of writing however, there are 60,933 compounds in the Materials Project database containing at least one of the alkalior alkali-earth metals, which is already unmanageable, without also accounting for electrides with cations outside of this group such as the confirmed electride 𝑌 5 𝑆𝑖 3 . 30 By contrast, the rule of total valence summing to plus one has recently become a viable screening tool for the first time. Ding et al. have reported scanning the inorganic crystal structure database (ICSD) 31 containing 169,800 materials, to find the oxidation states of 108 elements. They found that just 84 oxidation states could cover more than 90% of all reported charges in the ICSD. The small number of the probable oxidation states effectively reduces the combinatorial explosion of possibilities when matching elements to make compounds and allows for a most probably overall valence value to be calculated for a given chemical formula. Figure is found by taking the most probable oxidation states reported by Ding et al. to calculate the overall charge of all compounds in the Materials Project (including those not thermodynamically stable). The x-axis is the total valence of compounds, and the y axis is the number of the compounds corresponding to the total valence. As can be seen, there are around 4,000 compounds with an overall oxidation state of +1, which is a surprisingly large candidate pool for finding electrides but still much more manageable than the candidates approximated by the other two design rules. Naturally however, the overall largest assigned valence is zero by a wide margin, corroborating the results of the previous study and perhaps explaining the perceived rarity of electrides.