A feature on meta-sites (and apparently for high rep users) allows you to track your next tag badge. There is a recommended tag by default, which is supposed to be the tag you are closest to completing. How is this closeness calculated?
It seems to be based on both your current tag score and the number of answers provided, but how specifically does it achieve this? I'm just curious.
For reference, this question on Meta Stack Overflow inspired this question, and it also includes my best guess (which might be totally wrong).