I have observed in Stack Overflow that sometimes there are major differences between the number of questions shown for a given tag in the Tags page and the number of questions you see when filtering questions by the same tag.
I have observed the same behaviour, although not as evident, in other StackExchange sites as Server Fault.
This behaviour seems to become more evident the more questions the specific site has. For example:
- The SciFi site, with only 16322 questions, seems to be unaffected.
- Server Fault(182473 questions) seems to be beginning to be affected in some cases.
- Stack Overflow (over 8 million questions) seems to be more affected than Server Fault (although since I first asked the question number has changed a lot so I could not find as much examples as back then).
Some random examples from today:
- [security] (Stack Overflow): 28688 questions in Tags page and has 29805 questions tagged. Today 24 questions were asked.
- [visual-studio-2010] (Stack Overflow): 43021 questions in Tags page and has 43172 questions tagged. Today 23 questions were asked.
- [networking] (Server Fault): 8576 questions in Tags page and has 8554 questions tagged. Today 7 questions were asked.
- [linux] (Server Fault): 23817 questions in Tags page and has 23773 questions tagged. Today 12 questions were asked.
I guess that tag statistics are not real-time but calculated daily (nightly?) so that would account for a relatively small difference but not all of it.
Anyway, whatever it is, it is not site-specific or at least not Stack Overflow-specific.
Can anyone explain this behaviour?