Twitter By The Numbers

There have been a lot of statistics coming out lately about Twitter. I'm sure there will be more headlines about Twitter given today's little outage. What follows is a sampling of some various statistics that have been published lately.
Here are some stats from Sysomos about Twitter usage:
53% of Twitter users are women and 47% are men
72.5% of all users joining during the first five months of 2009
85.3% of all Twitter users post less than one update/day
21% of users have never posted a Tweet
93.6% of users have less than 100 followers, while 92.4% follow less than 100 people
5% of Twitter users account for 75% of all activity
48% of the most active users have more than 100 followers, compared with 6.3% for overall Twitter users
More than 50% of all updates are published using tools, mobile and Web-based, other than Twitter.com
TweetDeck is the most popular non-Twitter.com tool with 19.7% market share
Here are some stats from Nielsen about Twitter usage:
10.7% of all active Internet users used Twitter in June 2009
16% of Twitter users are under 25 years old
64% of Twitter users are 26 to 54 years old
It should be noted that Nielsen was only looking at Twitter.com users. That leaves out mobile phone and other application users from their statistics.