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9:50 AM
At the moment there are 845 questions with deprecated tags. (Or if we discount the migration stub which is going to be deleted eventually, then only 844.)
There were 904 questions with deprecated tags a year ago, which means decrease by 60 questions in one year.
There were 1000 such questions in August 2017, 900 such questions in June 2018.
You can also compare this with numbers from March 3, November 27, August 25, June 2.
with 308 questions, 174 if we omit the most frequent algebra-related top-leve tags and 97 questions with no top-level tags.
with 379 questions, 229 if we omit frequent geometry-related top-level tags and 132 with no top-level tags at all.
contains 159 questions, 75 if we omit co.combinatorics, 37 with no top-level tag at all.
Also deprecating of (convexity) was discussed on meta.
The are 155 questions where was removed, 735 questios where was removed 79 questions where was removed.
You can find queries returning those posts here: chat.stackexchange.com/transcript/message/49179918#49179918 You can even check which users have edited them away: chat.stackexchange.com/transcript/10243/2019/4/28
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 102082 questions on the site, 79600 questions without a top-level tag, 84539 questions if we also count (linear-algebra), (graph-theory) and (set-theory).
22.023% of questions without top-level tags, 17.185% of questions if we take the less strict interpretation.
Here are the links used to find the posts without top-level tags: chat.stackexchange.com/transcript/10243/2018/10/27
 

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