Firebolt: Ms. Rowling, after the first book, you stopped converting English words to American words. Is there any reason for this?
J. K. Rowling: Actually, we didn't stop, but the number of words that were changed has been greatly exaggerated! We only ever changed a word when it had a different meaning in “American,” for instance, the word “jumper,” which in England means “sweater” and here, I believe, is something that only little girls wear!
AOL interview with J. K. Rowling October 19, 2000