I gave away my books and sales increased
There are a number of claims that this happens in the academic market as well.<p>Sources:<p>1.  Peter Suber's Open Access monograph, chapter 5, p. 107-110 (itself open access, of course). <a href="https://cyber.harvard.edu/hoap/Open_Access_(the_book)" rel="nofollow">https://cyber.harvard.edu/hoap/Open_Access_(the_book)</a> argues that OA books facilitate "searching and sampling," and then people want to read the whole thing in the nicer print format.<p>2.  University of Michigan Press says it happens sometimes thanks to increased "awareness and visibility": <a href="https://www.press.umich.edu/openaccess" rel="nofollow">https://www.press.umich.edu/openaccess</a><p>3. A phd thesis reviewing studies, and finding a negative relationship between OA and sales: <a href="https://openaccess.leidenuniv.nl/handle/1887/68465" rel="nofollow">https://openaccess.leidenuniv.nl/handle/1887/68465</a><p>4.  A swiss study of matched pairs of books, one OA, one traditional; no statistically significant difference in sales <a href="http://www.snf.ch/SiteCollectionDocuments/OAPEN-CH_schlussbericht_en.pdf" rel="nofollow">http://www.snf.ch/SiteCollectionDocuments/OAPEN-CH_schlussbe...</a>