So, I have a reason to display percentages in the thousands and greater
1000%, 20000%, etc
should they be written with or without thousand separators?
1,000%, 20,000%, etc
I have been Googling and can't find an answer; I keep ending up on sites talking about Excel number formatting.
Best Answer
Numbers up to 9999, whether they are percentages or not, should not use a separator, and from 10,000 on should (and a comma is actually not standard, but it is still common).
I see five references on the first page of Googling for Numbers up to 9999 comma.
My reference to using a space separator corresponds to the SI standard, and, as mentioned in the comment, this is based upon ISO 31-0.
EDIT: I should say, in tabular form, such as in Excel of course, including the separator for 1,000-9,999 makes sense when there is likely to be numbers greater that 10,000.