As of October 2009, Twitter.com experienced user growth (measured by the number of new subscribers) of 200 percent over 2008 statistical data.

The following reported statistics count users who create and use accounts through Twitter. Statistics may be slightly higher as Tweet traffic is not counted for those who use services like TweetDeck, or automatic Tweets sent directly from blogs, or who access Twitter via mobile aps and text messages.

The following Twitter statistics count users aged 18 and older who visit or use Twitter at least once per month:

2008: 6.0 Million Users (11.1% of adult Internet users.)
2009: 18 Million Users (3.8% of adult Internet users.)
60% of Twitter users abandon their accounts within their first month of use.

Twitter’s retention rate is only 40% compared to MySpace and Facebook who enjoy a 70% user retention rate.

According to Mashable, Facebook “counts more than 250 million active users, 120 million of which they claim login at least once daily.”

2010: (Projected) 26 Million Users (15.5 % of adult internet users.)