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I am actually stil waiting for the final lists to ensure a comparable search result "study". Regarding subdomains & worst approach: thats whats confusing me (maybe due to my newbie status with seomoz): The domain authority for the TLD is lower than the ones for the subdomains. I actually figured this to be a hint, that subdomains do inherit this from the root domain. But I hope to be able to tell you more in 2-3 weeks, when I have those lists ready and can compare the search workds/phrases over all countries.