In the last eight years of its existence, Wikipedia has rapidly become one of the most used reference sources in the world. But a new study, conducted by researchers at the Palo Alto Research Center in California, has shown that Wikipedia’s rise to the top of a large pool of online reference sites may be coming to an end. New study shows that the website’s explosive growth is tailing off and the community-created encyclopaedia has become less welcoming to new contributors.

The research team has warned that the changes could compromise the encyclopedia’s quality in the long term. “It’s easy to say that Wikipedia will always be here. This research shows that is not a given,” New Scientist quoted Dr. Ed Chi, Senior Scientist at the Palo Alto Research Center.

Currently, Wikipedia contains nearly three million articles submitted by users themselves and edited by others in the Wikipedia community. However, when the Palo Alto team analyzed a downloaded version of the encyclopaedia, they found that its growth has peaked.

Researchers found out that the number of articles added per month flattened out at 60,000 in 2006 and have since declined by around a third. They also found that the number of edits made every month and the number of active editors both stopped growing the following year, flattening out at around 5.5 million and 750,000 respectively.

The data suggests that the Wikipedia community is not tolerant to new content and editors. Those casual contributors who make just a single edit per month, have 25 percent of their changes erased or modified by other or active editors, a proportion that in 2003 was 10 percent. The rate for editors who make between two and nine changes a month grew from five to 15 percent over the same period.

Chi wrote in his blog, “The changes could harm Wikipedia in the longer term by deterring new editors from taking part and so reducing the number of people available to spot and correct the vandalism that constantly threatens the encyclopaedia. Over time the quality may degrade.”

But one of the experts leading the review, Eugene Eric Kim of Blue Oxen Associates in San Francisco says that Chi’s arguments are only one of several possible explanations for the changes seen in Wikipedia. The high number of reverts, for example, may be due to the increasing use of spam software that inserts promotional text, such as links to company websites, into articles.

The Palo Alto team is likely to present their analysis at the ‘International Symposium on Wikis and Open Collaboration’ in Orlando, Florida this October.