One “variable” that has gone unmentioned has been the explosion (on en, at least) of the number of WikiProjects. To extend your Ann Arbor/Detroit analogy, I believe these provide “neighbourhoods” in which people can still feel a sense of community. They also provide (hopefully!) a welcoming place for newbies, and a place to organise quality improvement work.

Although a newbie may not get to create the NAFTA article, there is still a great sense of pride in turning that into a Featured article. Wikipedia may be maturing, but there still lots to do and it’s still an exciting place to work!

Your comments and others have brought to mind som ideas I’ve been kicking around regarding web 2.0 material.

1. What about The Wikilacrum, or the similar wiki sites that spring up that consolidate some of the more niche-oriented material that demands greater specialization and a more familiar knowledge of the material? I think Tgr is right about one thing, that specialized knowledge bases seek different tools and have different reasons for writing information.

2. Brandipedia.I am assuming that most people are like me. They may not be. But all I know of wikipedia is that it is a brand that challenges conventional thinking on resource material. If I was a resource creator by trade, I don’t think I would seek to access Wikipedia as a contributor. My resources and livelihood are tied up into other things, usually more “stable” and traditional. I know that’s assuming a lot, like, that other means other than Wikipedia are traditional.

3. In my opinion, it would be ridiculous to assume that Wikipedia could ever be finished and reach a plateau. That would go contrary to web 2.0 thinking. Although, whose to say that all web 2.0 sites act like other web 2.0 sites in terms of user behavior.

The final point I’d like to make is simply about what is natural intelligence and what is consumer-generated, or consumer-guided intelligence? Jimmy Wales had to sell the idea of Wikipedia before it became a useful alternative to encyclopedic discourse. Encyclopedic knowledge building has always been a revolutionary thing. Usually, manic and marginal individuals set out on journeys of mental discovery by catalouging everything they can in order to, well, find some kind of notoriety or success.

Is Wikipedia really a natural system? Or is it a successful project in non-profit consumerism?

To translate this and some earlier comments to research questions:
- what is the distribution of edit count in new content creation and new article creation? How much of that is done by anons? How does this distribution correlate with the size of a wiki?
- why do people leave? Maybe the software could send a mail to all editors with sufficiently high edit count who didn’t edit for, say, three months, and ask them to participate in a survey.
- in which wikis did the growth in articles change from exponential to slower, and when? How does that correlate with the number of people speaking that language? (Even better if internet/broadband access statistics can also be factored in somehow.) This might also be interesting to see for the number of editors and number of edits.
- was the smaller rate of new articles accompanied by a growth in quality? GA and assessments are probably too new to be useful, and FA is too much of a bottleneck, but mean article size might be a useful metric.
- what is the half-life of editors? how does it correlate with wiki size and with edit frequency? Is there a burnout effect (shorter halflife for very high-frequency edits)?

It would be really nice to see research done in these areas, maybe even funded by Wikimedia.

When I first read your post, I had a similar reaction to Geoff: there’s no one thing that has changed dramatically in terms of governance or community, while the logistically (low-hanging fruit) explanation has been predictable since even before the first signs started showing.

However, the (at the this point very limited) data shows too sharp a drop off for most reasonable “low-hanging fruit” models; I also suspect there’s more to it.

Jussi-Ville Heiskanen may be onto something; the reduced supply of low-hanging fruit could be compounding the learning curve for new editors at the same time that Wikipedia is nearing saturation in terms of exposure to likely editors. So the earlier generations of Wikipedians are fading away without smaller pools of new talent replacing them. (This brings up an important question: what is the half-life of a Wikipedian? My guess: about 2 years)

Another contribution might be the recent (and to some extent ongoing) notability reforms. Though the changes were not large, and actually eased the notability requirements, they also brought a lot more Wikipedians on board from the “inclusionist” end of the spectrum, meaning that more editors are willing to enforce (and encourage others to abide by) the notability guidelines.

The contention over BLP policy and its interpretation has pushed away some users, but I suspect that could only account for a tiny portion of the dropoff.

You suggest that “Perhaps the only virgin areas for Wikipedia are ones related to “newsmakers” or sudden celebrity.” Even in terms of news, there is plenty of notable material that does not get covered. For example, I’m perpetually disappointed in the Wikipedia coverage of pending and recently enacted U.S., and litigation of national significance. For most scholarly topics, even relatively well-covered areas like the sciences, the current Wikipedia coverage (in terms of number of potential articles) is still only scratching the surface. It’s just that the number of people both capable and willing to write any given missing article is small.

I agree with Kat that, prima facie, the dropoff in new article creation is not particularly worrying. The sooner there are no notable entertainment topics (besides the brand new ones) to start new articles on, the better off the Wikipedia community will be. The next step is to push forward with quality control mechanisms, to make Wikipedia more attractive to more of the kinds of editors who can pick the higher fruit.

arwiki also has especially much to offer in developing material on Arabic-related topics, places, etc, which often requires consulting Arabic-language sources. There’s a clear bias on enwiki towards the U.S., Europe, Australia, and such places, with other places covered more sparsely on enwiki and the whole of arwiki needing lots of work. There’s also a bias on enwiki towards pop culture, with some academic topics still needing much work.

Don’t know how much I’ll do on arwiki, as I’m not a native speaker. What I can do is help develop featured quality material on enwiki, and help translate featured articles from enwiki to arwiki. Someday, I would like to translate high quality material from arwiki to enwiki.

In all, what’s needed
(1) increasing participation on arwiki (and other wikis)
(2) reducing the bias on enwiki
(3) increasing number of featured articles on enwiki

These aren’t simple, easy things to do.