A stock market-style "happiness index" that measures the mood of the world on any given day using people's Twitter updates has been developed by US scientists.
Much in the same way the FTSE 100 index rises and falls, the happiness index - dubbed the "hedonometer" - shows peaks and troughs plotted on a graph.
But unlike the FTSE 100 index, the hedonometer represents the averaged out emotional state of tens of millions of people.
Mathematicians at the University of Vermont developed the index by collecting some 50 million tweets a day from around the world and analysing them for "happy", "sad" and "neutral" word content.
The hedonometer is based on a psychological assessment of around 10,000 words. Paid volunteers rated the words for their "emotional temperature", ranking the happiest at the top and the saddest at the bottom.
Words are then assigned scores - from one at the bottom to nine at the top - and from this an average happiness rating then is calculated and plotted on the graph.
- "Happy" = 8.30 on the happiness scale
- "Hahaha" = 7.94
- "Cherry" = 7.04
- "Pancake" = 6.96
- "And" = 5.22
- "The" = 4.98
- "Crash" = 2.60
- "War" - 1.80
- "Jail" = 1.76
"Reporters, policy makers, academics - anyone - can come to the site and see population-level responses to major events", Dr Chris Danforth, who helped develop the hedonometer, said.
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A dramatic dip in the hedonometer took place on Monday, April 15 - the day of the Boston Marathon bombings - showing how shock waves from such events resonate around the world.
According to the hedonometer, April 15, 2013, was the saddest day since the scientists started gathering their data five years ago.
Trending words such as "explosion", "victims" and "kill" pushed the happiness index down to its lowest ever level that day.
Positively scored words such as "prayers" and "families" also spiked that day - but not for positive reasons.
In the future the hedonometer will also utilise data from other online sources, including Google Trends, online blogs, and bit.ly links.