I got a royalty statement yesterday for How to Teach [Quantum] Physics to Your Dog (it continues to sell steadily, which is very gratifying), which includes a breakdown of the sales in terms of different formats. That reminded me of a particular annoying quirk of many recent discussions of the state of modern publishing, which is the often unsupported assertion that everything is ebooks these days, and paper books (and book stores) are just a small residual element that publishers and authors cling to out of historical affection.
Since I happen to have my royalty statements in front of me, let me add a bit of, if not data, at least more than one anecdote. I'm not going to give absolute sales numbers, because that seems to be one of those things that's Not Done, but for the last five royalty periods, here's the fraction of ebooks out of the total sales of How to Teach Physics to Your Dog
2014 Mar 0.20
2013 Sep 0.27
2013 Mar 0.15
2012 Sep 0.16
2012 Mar 0.25
That is, electronic versions account for between 15% and 27% of the total number of copies sold. The lower fractions in the royalty periods ending in September 2012 and March 2013 are probably due to discount sales of the hardcover as that was phased out-- hardcover sales are comparable in number to the ebooks in those two periods, but drop to zero for the most recent periods. (Prior to March 2012, the royalty statements are in a different format, and I can't be bothered to figure out where the ebook sales figures are.)
For How to Teach Relativity to Your Dog, I only have two periods of reasonably clean data-- the third one back has a bunch of returns (sigh) that skew the totals really badly.
2013 Dec 0.16
2013 Jun 0.19
So, that's basically consistent with the figures for the quantum book-- in the neighborhood of 20%.
Note that these are percentages of copies sold, not revenue. The fraction of revenue derived from ebook sales is difficult to calculate, because the ebooks are sold at a bunch of different price points, which one set of royalty statements reports on a separate line for each. The ebook price is generally a bit lower than the paper price, but my royalty rates for ebooks are considerably higher than for paper books, so it's probably a wash, more or less.
Now, of course, there are a lot of caveats to be applied here. The books in question were not new releases in any of these periods (How to Teach Relativity to Your Dog was released in Feb. 2012, which temporarily boosted sales of the quantum book, but they're from different publishers, so they weren't extensively cross-marketed or anything like that). Some of the low ebook fraction may reflect the awful discoverability of ebooks relative to paper books; a new release that was getting more prominent mentions on the electronic sales sites might move better than one that's off the front page, where you pretty much have to specifically search for the ebook to find it.
These are also non-fiction books, where most annoying arguments about ebooks focus on fiction sales. The two sides of the publishing business are very different in lots of ways, so I can't swear that these numbers would be reproduced in the novel sector.
You can also argue that this is a matter of pricing-- that if ebooks were just sold at the "right" price point of $cheaper, these numbers would reverse. Which, yeah, maybe. I don't see a very clear pattern in all the different price point figures on the royalty statements, but then they don't have the venue listed-- a $4.99 ebook sold direct from the publisher's web store is a very different thing than a $4.99 ebook sold via Amazon, and probably sells many fewer copies. Without the source data, there's no way to say.
But the take-away here should be pretty clear: while ebooks have made great strides in the last several years, paper books are very much Still A Thing. If you're talking about paper books as a basically negligible historical legacy, well, you really don't know what you're talking about. If you're lambasting publishers and authors for making decisions right now that give more weight to paper book sales than ebooks, you're ignoring current reality. I absolutely agree that in the medium-to-long-term ebooks will be increasingly important, but there's a long way to go before they're the most important factor to be considered.
(And, for the record, I have more or less stopped buying paper books in favor of ebooks, at least for myself. We still average something around two paper book purchases per week, as by standing agreement SteelyKid and The Pip are allowed to pick one book each when we go to the local indie bookstore on our Sunday morning market run. But this is a reminder that personal experience notwithstanding, ebook-only readers are not yet dominating the market.)
It's a question I don't quite know how to ask, but it's been bugging me: You're completely right in saying that in the current reality decision making has to focus on paper books because they are the majority of sales, but there's something that makes the issue confusing for me. It's not a system without a feedback loop. The return path gain may be small but it's there. If publishers decided to focus on ebook sales, if they set lower price points and removed DRM and importantly, focused their marketing efforts that way, if they tried to make ebooks more available in short... Well, maybe that would not tip the sales balance the other way still, in that case the effort may not be worth making. But not making any effort (or, well, doing things like colluding to keep ebook prices high) and then pointing out that they are right not to because ebooks form a minority of the sales---isn't that a bit of self-fulfilling prophecy?
(In the absence of market research and solid data, this is just me thinking out loud with no consequence. Potentially ignorable.)
It's a tricky problem; there's also the fact that 20% is not nothing when it comes to talking about revenue streams.
I don't have a great idea for how to address these issues, which is why I'm a guy who writes books and cashes the occasional royalty check, not an executive at a Big Five publisher. There does need to be some planning for the future, and it's not clear from the outside that they have any coherent idea about how to handle the shift to ebooks when it comes. There may well be people working on the problem whose efforts aren't public; I would hope so, but again, I sign the checks on the back, so I don't know.
My vague feeling is that while ebooks dominate in the sort of elite tech-y bubble I mostly operate in, the general market penetration of ebooks isn't as great as that might lead people to think. Which means there's less upside to making a major push to make ebooks more available than you might think. Five years from now, the story is probably very different, but I think these changes happen a lot more slowly than many of us realize.
FWIW, a less-anecdotal number from the APA is that ebooks "now [early 2014] account for 27% of all adult trade sales, up from 23% in 2012." So your numbers are on the low side, but not by too much.