That information is only available on careers profiles.
However, you can see the top 20 answerers in any tag. For C# for example, the following URL shows the current top 20, the top answerers for just the last 30 days, and the same information for questions:
Here you see Jon is not only listed in that ranking, he holds the top slot.
Any tag page has this linked to the top users page, here is the C# page link:
If you yourself have answered questions with this tag, your score will be listed, but it may be placed at the bottom if you don't otherwise are ranked. That way you can at least compare your own score with the top users and see if you are close yet.
For the c# tag, which I don't follow myself, I managed to gain 1 point (probably a Python answer that was also tagged with C#), so I am listed at the bottom. The answer is older than 30 days, so I am not listed in the 30 day ranks at all:
This is of course not the same thing by far, but is also more accurate than the percentage reading given on Careers. On Careers I rank in the 10% for the django tag for example, but I don't rank on that tag's top 20 users page; in fact I have quite a ways to go before I'd ever get there. But for all people listed on Careers that have answers in that tag, I apparently rank in the top 10%. Golly. :-)