Alphabetizing

Q. Is alphabetizing abbreviations based on the letters in the abbreviation or the letters in the spelled-out word? For example, does wthr (weather) come before wiki (Wikipedia)? Which is “correcter,” letter-by-letter alphabetizing or word-by-word?

A. Letter-by-letter. If someone is consulting the list, it’s probably because he wants to learn what an abbreviation stands for. It would be perverse to make him guess in order to find it.

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]