@Virginicus Well, doublets are weird :) And relatively rare, in my dataset I have only 130 doublets, in contrast to 3014 adjectives that occur only with -ity (1343) or only with -ness (1671). And finally, of course I had to check further for "electricness" :). It does not occur in my dataset, but in the Corpus of American English, there is a single hit, see below (with "electricity" ever so slightly more frequent, with 26014 hits :)).