Using Google’s Ngram Viewer, I’ve been having fun deducing all sorts of relationships. For example: if you know your history, you know that lithography wasn’t invented until the late 18th century and wasn’t really made use of until the early 19th century - hence the flatline at the beginning of this graph.
As handmade prints decline in use for book illustrations, we see lithography and woodcuts leveling out around the same small percentage. Looks like there are some interesting periods in the history of woodcuts, though - makes me want to read about them!
