DRM-free indie ebooks outsell DRM-locked ones 2:1

Author Earnings has published its latest eye-popping data-analysis of ebook sales and rankings on Amazon.

Amid the general growth of indie books (indie authors now make more as a group than Big 5 authors, though there are a lot more indies sharing that pie), there's this amazing fact:

It wasn't surprising to see that most Big 5 books employ DRM, but we were shocked to see that it is practically 100% of them. Indies, on the other hand, locked down roughly 50% of their titles. Since there isn't any variation in the Big 5 books, we are forced to look at the self-published titles for any effect on sales, and indeed there is one. The 50% of non-DRM ebooks account for 64% of total unit sales.

Indie titles without DRM sell twice as many copies each, on average, as those with DRM.

To confirm that this finding didn't simply reflect a correlation between ebook pricing and DRM election, rather than a consequence of DRM itself, we compared the average daily earnings of non-DRM titles to DRM titles at each pricing cohort.
At almost every price point, we see the thousands of titles without DRM significantly out-earning the thousands of titles with DRM. In fact, at the only two price points that appear to buck the general trend and which show DRM titles outselling non-DRM ones, we found that the reversal was due to 3 outlier DRM titles published by only two authors.

July 2014 Author Earnings Report

(Thanks, Chris!)