For the moment, I recommand to show on the Wikisource main page the "number of words". Erik Zachte just released new statistics for November 30 : http://stats.wikimedia.org/wikisource/EN/TablesDatabaseWords.htm It could be trusted. It would be :

1. EN : 235 M
2. FR : 142 M
3. ES : 47 M
4. ZH : 37 M (but I don't think this is correct : how do the stats count "words" for Chinese Wikisource ? There is another method : 1737 [number of bytes per article]/3 [a Chinese word is 3 bytes] * 42000 [number of articles] = 24.3 M)
4. RU = 27 M
6. IT = about 22 M (there is a problem with them. The stats say there were 12000 articles on November 30, but it is wrong. There were surely 18000 or 19000 articles, like now -> so the number of 14.4 M words should be risen with its half to 22 M)
7. AR = 21.6 (good surprise, but is it correct ?)
8. PL = 18.7 M
9. DE = 18 M
10. PT = 16 M

I feel sorry for the Germans. The low number must be the result of the total use of the "Page mode". We should ask to some developpers if counting the number of words in, for example, the "Proofread pages", could be possible. This number of words could then be added to the number above...