Upon reading this more carefully, I think there is something to note...

First, they do mention how brick-and-mortar sales in traditional publishing is as-much-as 50% of the sales an author will get. They handicap the results later on by basically doubling the revenue numbers of traditional publishing to account for this, at which point indie and traditional are more comparable ... but most of the graphs do not include this correction.

What they don't do at all, which seems necessary, is compensate for the difference in volume of the samples. If you look at the first appendix, they show that of the 1M titles they sampled, 13% are Big-5, and 31% are indie. This is important. They have twice as many samples of indie work, and yet all these graphs are only looking at total number of authors from a given category to make a certain amount of money. Of course there are more indie authors IN TOTAL making more money... there are more indie authors period!

The question is not about total number, it is about proportional number... in other words, does one publishing route give you a better overall chance of making money (for whatever complicated reasons). In order to answer this, we need to normalize the data set.

An easy way to do this is just to double the big-5 bars on the charts. 13% is about half of 31%, so really we want to know what we'd see in our totals if we had another 18% on our big-5 sample set. If we had twice as many big-5 titles as the data set currently has, we could expect twice as many authors in a particular category than we are counting currently.

Then you need to (slightly-less-than-)double the big-5 bars **again** to include the brick-and-mortar sales. Once you do double the bar twice over, it is no longer clear that indie publishing gives you any statistical advantage of making more money when compared to traditional publishing. It seems like your odds of being a major hit in either group are about the same, and maybe slightly less in indie. This also explains why traditional publishing is not out of business, which is a question I was curious about after reading the article the first time.

So I guess the moral of the story is, worry about writing a really good book instead of which method of publication to pursue ;-)

In any case, thanks again for sharing, this was a very interesting article.