Ebooks for free increasing sales?

A lot of us right now know about the controversy and questions of the future of publishing. If i was smart, I would be doing my research paper on the status of ebooks at the moment, and in the future, but I’m not smart. However, while looking for other things, I found an article that linked to a study. The study found that the short term sales of print books went up after a free online ebook was released.

Interestingly, when a book was released for free and for an indefinite time, it actually increased the sales by an average of 5%.  However, when Tor released an ebook for only a week, it decreased the sales of that book drastically.

Anyway, here is the summary of the study and here is the whole article, in case you are interested in reading on that.