How many novels include maps? For his 2013 monograph on fantasy maps and settings, Here Be Dragons, Stefan Ekman surveyed a random sample of 200 fantasy novels and found that about a third of them came with maps. Computational methods have now answered this question using a much bigger sample:

Digital humanities scholars from the Cornell Ann S. Bowers of Computing and Information Science have developed a computational system to mine maps from nearly 100,000 digitized books from the 19th and early 20th centuries, discovering that just 1.7% of novels include maps, mostly at the beginning or end, among other findings. 

They also discovered that 25% of maps in novels depict fictional settings, and military and detective fiction—not fantasy or science fiction—were the book genres most likely to contain a map, contrary to initial hunches.

Contrary to what I would have expected as well! See the article here (PDF). [Tara Calishain]