In 500 crossword puzzles syndicated by the Newspaper Enterprise Association, and published in the "Laramie Daily Boomerang" six days a week between October 24, 1976 and June 11, 1978 (about 20 consecutive months), the number of times each letter of the alphabet was used was tabulated. The statistical results are summarized in the table on the next page, and discussed in more detail below.
Hitchcock, John D.
"Crossword Puzzle Letter Frequencies,"
Word Ways: Vol. 12
, Article 5.
Available at: https://digitalcommons.butler.edu/wordways/vol12/iss1/5