So, here's the deal. I live in a fairly rural area, but am lucky enough to have a decent writers group nearby. This group is one of the largest in the state and as a part of its function, acts as an independent publisher for many of the authors involved with the group. Aside from publishing an anthology of work from authors "with ties to the state," I have seen several of my ...peers... publish their work through this imprint.
I hesitate on the term peers for two reasons: First, I am the youngest member of the group by roughly 25 years. Second: Unlike the other members of this group, I am much more interested in trade publishing than in self-publishing, specifically because of your blog post on some hard numbers. and this post also on sales figures.
That being said, one of my fellow writers was excited to report at our last meeting that he was close to selling 500 copies of his book. An accomplishment, to be sure, but a far cry from the 20,000 copies referenced above. During that conversation, the group turned to me and asked when I'd be ready to publish my work.
While the idea of seeing my work in print excites me, I'm not ready to jump into something just because I can. With that in mind, I asked the head of the group (the woman in charge of the imprint) whether she had a way of tracking book sales, or (more importantly) what numbers would a trade publishers see if they were to look at the books out group publishes?
The short answer was, she didn't know. The book my fellow writer is selling does have an ISBN, but is printed through Amazon's CreateSpace, and most of his sales are to local book stores, book fairs, or individuals at other events.
Are these numbers a trade publisher would be able to find later on if he eventually wanted to sign with an agent and ultimately a publisher? I told the group I'd do some research, and your blog was the first place I headed.
Short answer: If it has an ISBN. sales will get tracked (most likely).
Longer answer: Sales numbers are collected by a company. They don't get info from every cash register in the world, nor do they have agreements to collect that info from every store that sells books. That means their data is incomplete, thus you need to factor in a margin of error.
Generally we think of Bookscan numbers (that's what they're called) as about 70% accurate, but that can skew all the way down to 30% accurate with some kinds of books.
For example, books that are sold to libraries don't get counted. Books that speakers sell in the back of the room don't get counted. Books sold at some indies don't get counted. This article gives more detail on what gets missed.
So, if your book is sold at county fairs, and the local chamber of commerce, chances are that Bookscan will not pick it up.
However, there's another thing I always look at, and that's Amazon rankings. Amazon doesn't measure volume, it measures volatility. Not numbers but how how the book is selling in relation to other books in its category (and Amazon has some WEIRD categories.)
A book can sell 3 copies and be #1 in the category if the category is esoteric enough.
What I do though is look for OTHER books in the category and then search them on Bookscan. From that I can triangulate in on a number of sorts.
But truthfully, if we're looking at sales of anything less than five digits, I'm probably only looking up this info to amuse myself.
What this means for you: anything you publish on CreateSpace and has an ISBN number can be tracked, and the fewer the sales, the less accurate the reporting which is bad news for you.
If you want to publish professionally, you're better off to do anything like this under a pen name and then burn that identity like you are Jason Bourne on the run.