This an interesting addition to my line of thought which was, basically, "giving them away free is good PR" which, of course, drives attention and sales. If ev

This an interesting addition to my line of thought which was, basically, "giving them away free is good PR" which, of course, drives attention and sales. If every book publisher (say, in the tech industry) announced free books at the same time, would this person's sales have increased by the same amount? Almost certainly not. Would they have increased at all? .. probably? But your comment adds a new twist, which is the timing/price discrimination side, where, to run an experiment, we'd also have to control for works that were already out vs not, by running this experiment on new releases as well as works already available for sale for some amount of time.