What particular factors might have begun to inhibit participation in 2006, when we know it began to stagnate?

Long mail ahead -- bear with me!

It seems to me that either A) article creation tends to peak at a certain number of articles, supporting the "low-hanging fruit" hypothesis. Or B) article creation tends to peak after a certain period of time has passed, or is associated with some other variable, and is unrelated to the number of articles. Which would debunk "low-hanging fruit."

So, from Erik Zachte's stats pages: New article creation in enWP peaked in July 2006, when enWP had 1.2 million articles. And, new article creation in svWP peaked in May 2006, at 162K articles.

That suggests that A, low-hanging-fruit, is false. If we looked at other language versions, and saw new article creation peaking at widely varying article counts, then A would be, in my view, thoroughly debunked.

Which leaves us looking for a different cause. I would say that then would leave us with three possibilities.

B1) If new article creation peaked across all language versions more-or-less simultaneously (meaning, on the same date), then I can only imagine that the cause is somehow both external to us, and global. Examples: a global blossoming of interactive sites lured away our editors, or, a terrible global economic collapse meant people everywhere needed to focus solely on paid work. (A non-external hypthesis: I also speculate sometimes: if Jimmy talked publicly, a lot, about quality post-Siegenthaler, then maybe that somehow engendered a large global increase in restrictiveness inside the editing communities. I can't think of any internal factor but Jimmy that would potentially have that kind of large global impact.)

B2) If new article creation peaked for each language version at roughly the same time post-launch (like, launch + five-and-a-half months), that would support the idea that our editing communities have a natural internal lifecycle. (That wouldn't mean the "natural" lifecycle was necessarily a positive one, but it would suggest that the cause of the peak is internal to each editing community.) I have sometimes wondered whether online communities have a certain period of time (possibly varying according to the nature of the community) during which they either thrive or fail: maybe that's true, and we have some of each type.

B3) If new article creation peaked for English on July 2006, and peaked for other language versions within a year afterwards, that would suggest to me that other-language-versions were possibly modelling their behaviours on the behaviours in English, regardless of their suitability. So for example, if "low-hanging fruit" were true for English, and English responded with a number of behaviours (such as more deletionism, more emphasis on "quality," higher barriers to new article creation, new focus on multimedia, etc.) -- then perhaps other language-versions started adopting those same behaviours, accidentally triggering a premature peak of new article creation. That hypothesis has always sounded true to me (anecdotally, people in other language versions have told me stories that tend to support it), but Swedish new article creation peaking before English suggests that is not true.

Does anyone have time to look at the stats pages and check a few other random languages for the date on which new article creation peaked, and the number of articles at that point? Because I am provisionally thinking, based on the Swedish example, that "low-hanging fruit" is not true.