From this post: http://meta.stackexchange.com/questions/78048/enable-automatic-deletion-of-old-unanswered-zero-score-questions-after-a-year


> **If the question is more than `365` days old, and ...**
> 
> - has a score of 0 *or* a score of 1 with a deleted owner
> - has no answers
> - is not locked
> - has a viewcount ≤ the age of the question in days times 1.5
> - has ≤1 comments

**TL;DR** "Tumbleweed" Questions get automatically deleted as of May 2011