How is dark chocolate separated into accurate percentages?

I suspect the other 30% is made up of milk (or vegetable fat) and sugar. I once had 95%-cocoa dark chocolate and when I put it in my mouth it was like instant dehydration. Tasty, but the dryest thing I’ve ever had.

It should say “70% cocoa”, not “70% dark chocolate”. The word “dark” is generally used by manufacturers to mislead the general public. I don’t know what the 30% is in the real 70% cocoa.
http://www.fluther.com/106708/dark-chocolate-is-healthy-for-you-what-do-you-say-about/

Who might find more information on Dr. Mark Hyman’s site.
Flo is correct.

Oops, please read: “I don’t know what the 30% is” (last sentence, in my last comment above)

It’s a percentage by the mass of cocoa derived ingredients (chocolate liquor, cocoa butter and cocoa powder). The other ingredients are sugar, milk, and then any other types of flavourings… basically in the ingredients list that is not cocoa-derived.