I noticed that a percentile is placed at the top of my resume in Careers 2.0.
How are these percentiles calculated? Is there a certain threshold you need to be over in order for it to be displayed?
We take all the candidates in our system who rank for that tag, sort by their total score in the tag, and figure out where you fall (rounding down to the nearest 10%, and accounting for large blocks of users who all have the same score).
The key bit is "candidates in our system", which only includes people who have at least a total score of 5 in that tag. If we didn't do that, everyone would be in the top 10% because the long tail of users with a score of 1 or 0 is so long.
If you fall below the 60th percentile, we don't show it. Also, we're now only showing this on passive profiles because we realized that active users should be able to customize which tags are shown.
Based on david's answer, I created this script on SEDE to calculate your ranking percentile on a given tag.