TWITTER users send one billion tweets a week, according to new statistics released by the company to mark its fifth anniversary. Five years ago this week Jack Dorsey, Twitters co-founder and chairman, sent the first tweet, which said: inviting coworkers. To mark the popular services fifth anniversary, Twitter has released some recent statistics to illustrate its global usage. On average 140 million tweets are sent a day, which is up nearly 100 million on the amount posted on a daily basis a year ago. More than 460,000 new account have been added every day over the last month and the number of mobile Twitter users has increased by 182 per cent over the last year. However, the company has not revealed how many people actually use the service via their phones. The site has over 200 million registered accounts but Twitter has also not revealed how many of those are active. The company now employs 400 people. In 2008, only three years ago, it employed eight members of staff. Interestingly 456 tweets were sent per second when Michael Jackson died on June 25, 2009, which was a record high for the service. That record was broken in Japan four seconds after midnight on New Years Day 2011, when 6,939 tweets were sent in one second. Agencies