Amazon began a program on June 1 that will apparently run for two weeks. When you go to the Kindle home page, there’s a banner across the top reading “Sunshine Deals, Over 600 Books on Sale for $0.99, $1.99, and $2.99”.

These books are not from the big agency publishers, who set their own prices. Amazon apparently reached out to smaller publishers and worked out deals with them. Amazon could have simply cut these prices themselves, but doing that would require them to take a big margin hit. More likely, the markdown is being shared. (And, in addition, Amazon has plenty of books priced in that band all the time that could simply be featured in this promotion.)

Amazon gains a great price promotion. The publishers in question gain substantial additional visibility for their titles.

Fortunately, there is one entity tracking the impact of price on ebook sales able to tell us: this is having a real impact.

Dan Lubart of iobyte’s “eBook MarketView” blog tracks ebook sales rankings by price band at Amazon. (He tracks it at other retailers too, but, in this case, Amazon is the one that matters.) Dan’s graph tracking the average price of Kindle bestsellers shows a pronounced impact from this promotion.

The average daily price of Kindle bestsellers took a leap on March 1 when Random House moved to agency and a whole slew of bestselling titles could no longer be discounted by Amazon. The Sunshine promotion has very suddenly brought that average bestseller price down to about where it was on March 1!

Dan has another chart showing the distribution of bestsellers among four price bands: up to $2.99, $3-$7.99, $8-$9.99, and $10 and up. Most agency-priced ebooks of titles whose currently available print versions are hardcovers are in the top two price bands. Since the promotion began, the number of bestsellers in the cheapest band has grown from 31 to 47. (He’s charting the top 100, taking out anything that he recognizes as “not a book.”) Half of the increase came out of the top-priced band with the other half distributed between the middle two bands.

In a conversation with Dan about this research, he pointed out that what he’s tracking is ranking, not sales. The movement of titles on and off and up and down on the bestseller list (top 100 rankings) doesn’t tell us anything about unit sales. That’s the piece of the puzzle that the publishers do know (for their own books).

There are a some critical points here, all of which are more important than they are surprising.

1. Amazon can create pricing promotions that will have an immediate and dramatic impact on the ebook bestseller list. (We observed three months ago that publishers might suddenly have a pricing problem with bestseller lists.)

2. Agency publishers are disadvantaged by this fact. The only way they can participate in a price promotion with Amazon is if they lower their agency price across all retailers (which isn’t going to be that exciting to Amazon). On the other hand, publishers on wholesale terms have much more flexibility to “buy into” a promotion (although that flexibility isn’t complete: Robinson-Patman would probably require them to participate in similar promotions with other retailers if other retailers wanted to create them).

3. Since Amazon has demonstrated so clearly that price has a major impact on ebook sales, and since agency publishers can control their prices, it follows that agency publishers need to be experimenting with the impact of price promotion (as self-published authors have already been doing, by the way).

But experimentation only makes sense if you can evaluate the results of what you test. As far as we know, the iobyte database is the only tool that exists right now to help publishers do that. That’s why we’ve started to work with Dan to introduce what he’s doing into the routines and workflows of the major houses.

One observer of Amazon’s new program speculated that it might be a step toward “dynamic pricing”, which is what airlines and hotels use to maximize their revenues for seats and rooms. I’m not sure that forecast makes sense. Airline seats and hotel rooms are limited in number; if you sell one too cheap, you can’t sell it to the next person for more money.

But ebooks are infinitely replicable. The trick for the airlines and hotels is to maximize revenue over a limited — fixed — number of sales. The trick for publishers is to maximize revenues over an unlimited — variable — number of sales. Cutting price to get on a bestseller list that might increase discovery and awareness and maybe generate sales at a newly-raised price is a tactic that almost certainly should be routinely, but not capriciously, employed.

It can’t be a good thing for agency publishers if the only price promoting taking place is with their competitors’ books.

I also discovered looking closely at this promotion that Amazon is not flawless. When I go to the Kindle store on my iPhone and tap on the Sunshine deals, I find lots of agency books listed, which, of course, are not price-promoted. Obviously a mistake — and from my experience a pretty rare one — by the folks at Amazon. (Since I know there are a few readers of The Shatzkin Files in Seattle, perhaps this will be corrected before you have the chance to see it but I first noticed it yesterday — Saturday — and it is still that way as I post much later in the day on Sunday.)