That last meta post about the [outdated answers project](https://meta.stackoverflow.com/questions/405302/introducing-outdated-answers-project) got me thinking. It mostly deals with identifying outdated content as well as what possibly can be done about it (including unpinning accepted answers, adding version (range) tags, adding warnings,...). The underlying concern is that the content of Stack Overflow ages and therefore quality and usefulness of the content and the order/way in which it is presented is reduced over time. People might not be able to quickly find working solutions to their problems anymore.

I wonder how we could best measure the success of any action that might be taken to do something about the problem of answers becoming outdated?

* Visits to Stack Overflow might surely be an important indicator, but it's very general and may change only slowly. The signal that is contained might be drowned by other influences.
* Time spent on pages might not be clear-cut enough. A longer time might indicate that more good content was found or that the search to find the good content took longer. A shorter time might indicate that good content was found quicker or that no good content was found at all.
* Ideally, you would find only useful answers among the top sorted answers or enough guidance to find useful answers and in the end, the useful answer (s) get upvoted. An upvote for an answer that is not shown on top of the sort order might indicate a miss sorting or it might indicate a new answer rising up to the top or that you had a legacy problem being solved by a now outdated answer, again maybe not clear-cut enough.
* There could be surveys like "have you noticed new feature X? Do you think it improves finding answers?" Or similar but then we would go away from hard numbers to interpretations. Might though be the most practical thing possible?

I'm running out of ideas here, so I ask the community how would you convince somebody with a suitable metric that a new feature X (unpinning of accepted answers, adding version (range) tags, adding warnings to answers, ...) really improves the ability of visitors to quickly find working solutions to their problems?

Searching for "measure success of" or "metric of" and "find the right answer" or "solve the problem" on meta didn't result in anything relevant regarding how to measure the effectiveness of actions.