Our style on “percent” is to spell out the word instead of using the symbol. Use the symbol only in statistical copy or in tables and graphs when you just can’t avoid it. Always use numerals with the word “percent.”
For example: “50 percent,” not “fifty percent” or “50%” and definitely not “fifty %” (oh, the horror!).
Why, you may ask — especially when that little “%” is so cute and you think it may add visual oomph to a text block? Here’s why: The preferred style is easier on a reader’s eyes and makes it easier for them to quickly pick up the meaning of the statement. A “%” is a visual speed bump that interrupts the flow of a sentence. Also, using “%” will make devout followers of AP style shred their garments and gnash their teeth. And who wants to see that?