Word popularity (frequency) is taken from the COCA website: Davies, Mark. (2011) Word frequency data from the Corpus of Contemporary American English (COCA). Downloaded from https://www.wordfrequency.info/ on January 01, 2012.
Less-common words are appended to the COCA list.
Word popularity (frequency) is estimated through a review of words found in the top 100 books on the wonderful Project Gutenberg website on a particular day. We download those books, break out the words, skip anything with a dash or apostrophe, make it all lower case (not CAPS), and count them. Finally, in our word list files, the words are ordered with the most common words first.