The key disconnect is that some people believe tradpubs select books for quality. That happens not to be the case at all.
Tradpubs select books they *think* will sell.
As eschwartz said, that criterion is orthogonal to the quality criterion.
Which is why the numbers I quoted were *sales* numbers. Indies as a category outperform tradpubs as a unit at what the tradpubs aim to achieve. As a matter of fact, many Indies choose not to stoop to meeting tradpub standards but instead aim for a higher, better standard: writing books they believe in first and then looking for an audience that can appreciate the story.
KKR said it best just last week:
http://kriswrites.com/2016/01/06/bus...usiness-model/
Tradpub criteria is far from the highest standard of quality, primarily because it isn't a standard of quality. Again, check out the Agent's view I linked to earlier. Tradpubs are all about sales. They give lip service to quality and culture but that is just talk.
Come crunch time they will publish ghost-written political "memoirs", adult coloring books, celebrity tattletales, and any other junk that might be in fashion for a week or three.
Once in a while, they will publish a book that is actually good but that is just as likely to be by accident as by intent.