The WoW census showed the total number of players in each faction, per each race, and per each class who self-reported via the CensusPlus AddOn, which scans players around the mod's player character. The Census only includes characters that are level 10 or higher and that have been active within the past 30 days. Unfortunately, the popularity of this AddOn has gone down dramatically since 2010, so it's data is mostly only useful for ratios.