I've never seen that notation in my entire life. Learn something new every day.

Just want to point out that you didn't call that out explicitly. 99% (note that it's a percent) of people who saw your comment would see it and view it as a percent. I did, and I work with data all day every day.

It's unintentionally misleading to use notation like that without calling it out.

Just type "per mille" next time.

You're right, I should have called it out in the text. I thought ‰ was okay because I was comparing the other cities to NYC, not to an absolute value. Also, I think it's a fun symbol, and I want more english speakers to use it.

Ahh, today i learned