Global 'happiness index' now online
A Footsie-style "happiness index" that measures the mood of the world on any given day can now be accessed by anyone online.
Click on www.hedonometer.org and you can see a wavy line plotted on a graph that rises and falls, in much the same way as the FTSE 100 index.
But the peaks and troughs have nothing to do with the financial health of major companies. Instead, they represent the averaged out emotional state of tens of millions of people.
A team of US scientists constructed the hedonometer from data obtained from the social messaging site Twitter.
Some 50 million tweets from around the world are collected each day and analysed for "happy", "sad" and "neutral" word content.
Words are assigned scores with the happiest and most positive placed at the top of a 1 - 9 scale. From this, an average happiness rating is calculated and plotted.
"Reporters, policymakers, academics - anyone - can come to the site and see population-level responses to major events," said Dr Chris Danforth, from the University of Vermont, one of two US mathematicians who developed the hedonometer.
The team hit the headlines in February after revealing Napa, in the heart of California's wine-growing region, to be the happiest city in the US. But the global website, providing a way to gauge the happiness of the world, has now gone public.
A dramatic hedonometer dip can be seen on Monday, April 15, the day of the Boston marathon bombings - showing how shock waves from such events resonate around the world. In fact, April 15 2013, turns out to be the saddest day since the scientists started gathering their data five years ago.
Soon the hedonometer will be using data from other sources besides Twitter, including Google Trends, the New York Times, online blogs, CNN transcripts and text captured by the link-shortening service Bitly. It will also be mining data in 12 languages.