Not economic for a professional author. But maybe just acceptable for an academic who wants the prestige or an idealistic teacher improving material for students. An author was button-holed by an admiring teacher. I liked your text-book so much I photocopied pages of it for my students. In that case, maybe I won t be able to buy enough time to write another one, was what the author thought, but didn t say.
Fewer courses prescribe texts.
Bigger books to cover diversity of course options. Electronic retrieval via off-campus screens reduce tertiary book sales. Continued secondary and primary textbook sales. A best-selling text sells 50,000 to 100,000 copies in its 10 year life. Uneconomic for a teacher-author to write texts requiring substantial research time for peripheral subjects or courses with multiple options.