From one of our amazing readers: Pew Research published research on Twitter users in February 2009:
http://pewresearch.org/pubs/1117/twitter-tweet-users-demographics. Not surprisingly, they found that young adults (18-24) are the heaviest adopters. The researcher also points out that lower income households are
more likely to have Twitter users: “17% of internet users in households earning less than $30,000 tweet … compared with 10% of those earning more than $75,000 annually”.
However, the Twitter landscape is changing quickly and analysis performed at different times can result in varying conclusions about user demographics. Blogging in March 2009, Nick Burcher provided more Twitter data:
Both Burcher and Pew show data that points to Twitter users being from diverse communities, reflecting the demographics of the younger population of the U.S. And don’t forget that Twitter is used in multiple countries.
U.S. users are only 40% of the entire Twitter user population.