Slightly more philosophy books were published in North America in 2013 (the last year for which there is complete information) than in each of the previous four years, according to data from Humanities Indicators, a project of the American Academy of Arts and Sciences. In the same year, philosophy ranked 7th in numbers of books published among the 8 humanities disciplines surveyed, as the graph below shows:
In total 54,273 books in the humanities were published in 2013. Further data is here.
(It might be interesting to figure out how the humanities disciplines compare in book production on a per capita basis. For that we’d need the number of people working in each of the disciplines, and I do not have that data handy.)
Thanks to Robert Townsend for the information.