Just to be perfectly clear, these numbers aren’t the real ones. They’re just an example of how startling they might be. But it made me wonder: is there a way to guess what the numbers might really be?

Well, I’m about to try. My process will be quick and dirty, but I think we might be able to ballpark it.

First off, David Gaughran has estimated indie books make up 30% or more of Amazon’s numerous bestseller lists. His work was indirectly backed up by a press release from Nook Press that 25% of their sales were indie. Another recent quote from Kobo put their indie authors at 20% of total unit sales, but they’re the new kids on the block and their discoverability isn’t all that great yet. I’m sticking with 25%.

Next, let’s look at potential earnings. How many sales does it take to earn, say, $1000 a month? For a $4.99 book (a little on the high end, for indies, but common enough), your royalties at 70% are going to be $3.50. Not all sales are at 70%–some are to markets that only pay 35%, like Australia. Up to 10% of my sales are to 35%-royalty territories. Treating that as a rule of thumb, we need to adjust our $3.50 figure, multiplying it by 0.95. In other words, for every sale of a $4.99 book, the author can expect to take home about $3.33.

Neat how that works out, because $1000 / $3.33 = 300 sales/month. 10/day. On Amazon.com, selling 10 books/day will give you a Kindle rank of about #12,000.

So at any given moment, 12,000 books are hitting that baseline of 300/month. And maybe something like 25% of those titles are indie. Meaning, at any given moment, something like 3000 indie books are earning $1000+/month on Amazon.com.

Upping it to $2000 means 600 copies/month, or 20/day, or a rank of #6000. 25% of 6000 = 1500 indie books earning $2000+/month.

To make $5000 at $4.99, a book has to sell 1500/month, or 50/day, or maintain a rank of about #2200-2400ish. So maybe something like 600 indie books are earning $5000 or more during any given month.

Note I’m saying “books,” not “authors.” That’s because translating this from books –> authors is very complicated and I’m not sure I can take a reasonable stab at it. But let’s pretend, for the moment, the two are equivalent.

Now, the numbers above are just for Amazon.com. Amazon UK is something like 15% the size of the US store. Amazon DE is an order of magnitude smaller, and the other stores barely register (for indie English-language sales, anyway), so let’s lump them all together and call it an extra 20%. That gives us the following numbers:

• ~3600 KDP books might make $1000+/month

• Of those, ~1800 might make $2000+/month

• And ~720 indie titles might make $5000+/month

These numbers look a lot smaller than PG’s, both in quantity and in income brackets, and this is with a price of $4.99, which is higher than most indie books. But here is the giant, messy, complicating favor that I have so far avoided like the plague: most successful indie authors have more than one book. Most have three or seven or twenty. That means the 3600 books capable of making $1000/month are unlikely to be doing so for 3600 different authors. The real number is more like, I don’t know, 1500-2500 authors.

But this also means many indie authors are capable of making nontrivial money with ranks much worse than #12,000. They just have to have more than one book.

Taking a stab at all that is.. daunting. But before I see if I can do that–which will require another post–let’s work with the numbers we do have some more. Because Amazon isn’t the only game in town.

In fact, conventional wisdom says they have 60% of the US ebook market. If so, by comparison, B&N has maybe 10-12%. I don’t know how many indies make up the remaining ~30%, but let’s pretend that indies have a quarter of those markets, too. Probably generous, but what can you do. Research, I guess.

So if Amazon is 60% of the US market, let’s take our Amazon.com number of 3000 indie books earning $1000+ and prorate that across the rest of the market by multiplying by 1.67. That gives us 5000. If we rashly assume that non-American English markets follow Amazon’s trends, and we add 20%, that bumps it up to 6000. Across the English-language indie ebook spectrum, then, we might have something like this:

• 6000 indie books might make $1000+/month

• Of those, 3000 might make $2000+/month

• And about 1200 indie titles might make $5000+/month

Now, this is really, really casual math. It requires a lot of assumptions and a lot of multiplying, which means that any mistakes are compounded. So don’t treat it as gospel. It’s just a rough stab.

And it’s possible these numbers are a fraction of the indie authors making a decent to significant income off their writing. Not only do most indies have multiple books–I didn’t account for any books making less than $1000/month, but ten books at $100/month will earn you the exact same money–but all these figures have been drawn from the lowest ends of the scale. If a #2000 rank is good for $5000/month, that means about 500 indie books are doing that well on Amazon–but the ones on the upper end are doing much, much better. An indie with a $2.99 book ranked #100 is making something along the lines of $1000-1500 a day.

Much of that top money will wind up repeatedly skewed to the top indies, of course. But for illustrative purposes, if you can launch a new $2.99 book to #100 and stick it there for 30 days, you’ve just made something like $30,000, minimum. On one book for one month. It doesn’t have to sell a single extra copy for you to get by for the next year in most parts of the US.

This process and more modest versions of it happen on Amazon every day. You put out a new release, and (if it sells fairly well) Amazon promotes it for thirty days; a few weeks or months later, it (generally) slides down the charts, maybe until it’s down there where no one can see it. It would be largely unaccounted-for in the methodology I put together here.

I don’t know how to account for that (or for the “most authors have multiple books” problem, which cuts both ways). But I think that, at a conservative estimate, it’s likely that at least 10,000 indie authors are making at least a part-time wage from their writing. And it could be a whole lot more.

I don’t know how that compares to the population of traditional authors, either. But if nothing else, there’s evidence that the indie revolution has provided a career for thousands and thousands of writers who didn’t have one before.

And that’s pretty cool.

ETA: An earlier version of this post put the $5000+ club at 1500, not 1200. But let’s not allow my failure at basic multiplication to detract from the credibility of this post!

As long as I’m adding this postscript, I should note that one of the reasons I show my work is so other people can identify any errors (and so people can tweak the sliders, should they disagree with my assumptions). If you think I’ve made an error, or you’ve got an idea for how to attack more complex problems like the “multiple books” issue, please speak up!