Quoting Bnoopy (by the way, wtf is a Bnoopy??):
57% of Amazon’s sales come from books you can’t even buy at a Barnes and Noble (to be fair, there is some skepticism around this number voiced here). This runs totally counter to the traditional 80/20 rule in retailing – that 80% of your sales come from 20% of your inventory. In Amazon’s case, 57% of their book revenue comes from 0% of Barnes and Nobles inventory.
First things first, turns on that 57% is more like 25-30% (says Jeff Bezos). Secondly, does this really "run totally counter to the traditional 80-20 rule"?
I don't think it does at all - or at least, you can't say that it does just by comparing Amazon's and Barnes & Noble's inventory. What does the fact that 30% of Amazon's sales come from books that are unavailable at B&N mean?
If you look at Amazon's inventory (~2.3M books), they have about 400K books available in their top 20%. While at the same time, B&N only has 130K books period. So Amazon could have well over 100% of its sales come outside of B&N's inventory and yet still not be outside of their top 20%.
Is that correct or am I missing something?