We conduct analysis on all of the predicted electride materials that were screened using our method. Firstly, we can consider the design principle of electropositive elements; thus the statistics on the composed elements of these 51 candidates are shown in Figure . The electrides are mostly composed of Lanthanides (26.6%) and transition metals (26.6%). For the lanthanides this is perhaps unsurprising as they are relatively electropositive and are unlikely to take back the anionic electron. The prevalence of transition metals is quite surprising by contrast as transition metals can often present multiple valences and therefore should be able to accept the electron back from the crystal structure. It was only recently that the first redox active electride was reported with the transition metal chromium in the compound Sr3CrN3. In the Sr3CrN3 electride the Cr exhibits a +4 charge but it is commonly reported as stable at +3, thus it defied expectations by not reclaiming the free Please do not adjust margins Please do not adjust margins electron in the crystal structure. Furthermore 16% and 10.6% of electrides are composed of alkali metal and alkali earth metal, respectively, which is a return to expected behaviour in line with extant design principles.