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3:11 PM
Now there are 750 questions with deprecated tags. You can compare this with numbers from December 23, August 25, June 2, May 1, etc.
There were 1000 such questions in August 2017, 872 about a year ago.
with 238 questions, 125 if we omit the most frequent algebra-related top-level tags and 57 questions with no top-level tags.
with 363 questions, 213 if we omit frequent geometry-related top-level tags and 116 with no top-level tags at all.
contains 149 questions, 67 if we omit co.combinatorics, 30 with no top-level tag at all.
Also deprecating of (convexity) was discussed on meta. It was also suggested to deprecate (continuity).
There are 246 questions where was removed, 770 questions where was removed, 102 questions where was removed, 228 questions where questions where was removed.
Some time ago I have posted also short analysis checking how many users contributed to the removal of the deprecated tags: chat.stackexchange.com/transcript/10243/2019/6/15
As I have mentioned before, it would be not difficult to prevent deprecated tags at least from being added to new questions: The existing deprecated tags should be blacklisted and Blacklisting (deprecated) tag while they still exist.
There are 110984 questions on the site, 86540 questions with a top-level tag, 91866 questions if we also count (linear-algebra), (graph-theory) and (set-theory).
22.025% of questions without top-level tags, 17.226% of questions if we take the less strict interpretation.
Here are the links used to find the posts with top-level tags: chat.stackexchange.com/transcript/10243/2018/10/27
 

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