It’s not just relatively low retention rates that Twitter has to deal with. Turns out, according to a Harvard Business School study, that the median number of messages a Twitter user sends—ever—is one. The researchers found that a small group is sending out most of the tweets on the service. Ten percent of Twitter users account for more than 90 percent of messages. That’s more than on the typical social network or on Wikipedia, where 15 percent account for 90 percent of entries. The implication, according to the Harvard researchers: Twitter “resembles more of a one-way, one-to-many publishing service more than a two-way, peer-to-peer communication network.”

SEE ALSO: Twitter Executive Talks About Keeping Tweeters From Leaving

Twitter executives have said they working to keep Tweeters engaged with the service. Last month, a study found that 60 percent of new Tweeters abandon Twitter.com after a month.

Click on the image below to see a larger image showing the Harvard study’s findings: