Late last year, Jean-Baptiste Michel and co-authors made public the Google Books Ngram Viewer, which graphically displays the rates at which words appear in the Google Books database over time. So, for example, one might compare Descartes vs. Nietzsche in English (click to enlarge):
Now, earlier in 2010, I had run a series of posts on what I call "discussion arcs", using as my measure the rate at which terms appear in keyword searches in the Philosophers Index database, over time. Naturally, it occurred to me to wonder whether the Ngram would deliver similar results.
It does not.
Some obvious differences are Ngram's broader expanse of time and the difference between the whole universe of books as a database vs. just philosophy sources -- especially the potential swamping of philosophy sources with non-philosophy sources. But even if we confine the search terms to names of philosophers that are distinctive enough so that we can assume that the references are mostly to those specific philosophers, there are important differences between the results.
Here's one: In one post, I noticed that most philosophers tend to have peak discussion in the Philosophers Index around age 55-70, while others (like Heidegger and Wittgenstein) seem to break away from the pack, without slumping in discussion. See these two graphs of fading philosophers:
[Updated March 7]