아이튠 공식 사이트는 아닌데 몇개국 정보만 제공하는 사이트네요.
http://www.itunescharts.net/faqs/#faq4

이 사이트 faq에

How are these charts calculated?

The short answer is "we don't know". They're calculated and compiled by iTunes, we can only assume they're based on downloads. Given that the published charts are presented as "live" rather than covering any specified timeslot, there's obviously some kind of algorithm at play, but beyond that it's anybody's guess. Podcast charts are slightly different since these are charts of "channels" producing content on a rolling basis, rather than a finished product like an album or a song. Again, the chart is most likely based on downloads but may also be based on new subscriptions too.

이런 중간 사이트 관리자도 잘 모를 정도면 공식적으로 공개된 정보는 없는게 아닐까 싶네요


애플차트는... 아이튠스 차트보다도 더 정보가 없네요 ㅡ.ㅡ;;

그냥 멋대로 차트였군요..ㅋ