What about utilities? Do they follow a similar trend?
The majority of Utilities don't have release dates on file here, so there is no way to know.
Could translations be going up and down due to both availability of translators to work on stuff as well as older ROM hackers slowing down (ahem ) for various reasons, before skilled newcomers coming up?
Sure. Also, the data is also skewed by the fact that it is based on the release date of the current version of any given translation, which can be significantly newer then the originally release counting for later years instead.