A group of academics at Imperial have created a tool that is able to rank the most influential speakers on any topic. This is achieved by scoring the users of Twittter; it is known as the T-index and is dependent on many times they post and are retweeted. The T-index is defined separately for each topic of interest. A high score is achieved when the user is well known and when they have been tweeted often. It is hoped the T-index will help advertising companies, political groups and digital agencies to ascertain who the most influential people are on social media. The tool was launched by sharing the ’10 most influential tweeters’ on five different subjects. The analysis has been done on topics such as Manchester United and David Cameron. The team who created it would like to expand the project so that any person can search who the most influential speakers are on any subject by themselves. The Director of the Institute of Global Health Innovation at Imperial, Professor Lord Ara Darzi, stated: “‘We first became interested in measuring influence in social media during the recent reforms in the health service, when it became clear that Twitter had become an important forum for discussions about the changes. We wanted to find some way of determining how influential different individuals were who were tweeting about the reforms and published a research article detailing our findings. “We then realised this metric could be more widely used across Twitter to measure key influencers in any topic from fashion brands, to public events to major geopolitical events. The results we’re getting from the topics we’ve analysed so far are fascinating, and certainly tell us more than existing metrics of influence currently in use.” Dr Dominic King, a lecturer at Imperial commented that “There are lots of companies that measure influence on Twitter, but they usually don’t tell you how they do it. They also focus on the individual rather than a topic.” “The T-index is a simple, transparent score that measures how influential someone is based on the quality and quantity of their output on a specific subject. The method is open to everyone, so people can discuss how useful it is as a metric. “The results show that bloggers and independent voices can have their messages disseminated to a wider audience than established news providers. For tweets about David Cameron, Marcus Chown and Chunky Mark have higher T-indexes than established media providers like the Guardian and Daily Mirror. “We also provide information on the most popular tweets overall about each topic. These are almost always from celebrities such as Stephen Fry, Lady Gaga or members of One Direction. But while one tweet about a topic may stimulate a peak of interest, it’s likely to be short-term. The T-index measures sustained influence.”