Recently I am reading a book and I found there are lots of words I rarely saw. While I was searching their meaning, I found that for a single vocabulary google has a
use over time for: statistic -- from 1800 to 2010.
I may imagine how google could gather the frequency that a vocabulary to be used in Internet. But what about before the Internet? How they know the frequency of the people in 1800 using a vocabulary? Does they first convert the chartaceous material into digital data then computing for the result or something else?