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.

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global happiness index

Global 'Happiness Index'

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, only went public today.

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.

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  • "Choose love over being right." -- <a href="https://twitter.com/Deepakchopra">Deepak Chopra</a>, author of <a href="http://www.amazon.com/Spiritual-Solutions-Answers-Greatest-Challenges/dp/0307719170/ref=sr_1_5?s=books&ie=UTF8&qid=1361917343&sr=1-5&keywords=deepak+chopra">Spiritual Solutions: Answers to Life's Greatest Challenges</a>

  • "Happiness is a choice you make. Every thought you have is a decision and in any given moment you can decide to be fearful or you can decide to be happy. Through gratitude, forgiveness and a commitment to peace you can choose to be happy." -- <a href="https://twitter.com/GabbyBernstein">Gabrielle Bernstein</a>, author of <a href="http://www.amazon.com/s/?ie=UTF8&keywords=may+cause+miracles&tag=googhydr-20&index=aps&hvadid=14473018884&hvpos=1t1&hvexid=&hvnetw=g&hvrand=18127529691149555283&hvpone=&hvptwo=&hvqmt=e&ref=pd_sl_2vtwtgsv5r_e">May Cause Miracles</a>

  • "Accept yourself, and expect more from yourself." -- <a href="https://twitter.com/gretchenrubin">Gretchen Rubin</a>, author of <a href="http://www.amazon.com/Happiness-Project-Morning-Aristotle-Generally/dp/006158326X/ref=la_B001IZTAPW_1_1?ie=UTF8&qid=1361916564&sr=1-1">The Happiness Project</a>

  • "Count your blessings ... pray every day ... honor God by taking care of your body and mind ... remove all negative people from your life ... learn to forgive yourself and others ... watch as many sun rises and sunsets as you can." -- <a href="https://twitter.com/TheWeightSaint">Richard Simmons</a>, American fitness personality and motivator

  • "The constant pursuit of happiness will lead to disappointment because happiness is not sustainable. BUT gratitude, acceptance, peace and loving are. Pursue those qualities and you will discover that you are happy a lot more often!!" -- <a href="https://twitter.com/christinhassler">Christine Hassler</a>, author of <a href="http://www.amazon.com/20-Something-20-Everything-Quarter-life-Balance-Direction/dp/157731476X/ref=sr_1_1?s=books&ie=UTF8&qid=1361917126&sr=1-1&keywords=christine+hassler">20-Something, 20-Everything: A Quarter-life Woman's Guide to Balance and Direction</a>

  • "Trust yourself. If you don't learn to trust yourself, you will never be happy. You'll always be deferring your authority to someone or something outside of you." --<a href="https://twitter.com/PaulSelig">Paul Selig</a>, author of <a href="http://www.amazon.com/Am-Word-Guide-Consciousness-Transitioning/dp/1585427934/ref=sr_1_3?s=books&ie=UTF8&qid=1362024035&sr=1-3&keywords=paul+selig">I Am the Word: A Guide to the Consciousness of Man's Self in a Transitioning Time</a>

  • "Nothing has meaning besides the meaning we give it! It's not about 'positive thinking,' it's about 'powerful thinking' -- realize that in any given moment, you can choose to find an empowering meaning in every situation -- one that puts you in a space of love, hope and happiness." -- <a href="https://twitter.com/marieforleo">Marie Forleo</a>, marketing and lifestyle expert, founder of <a href="http://rhhbschool.com/">Rich, Happy & Hot</a>

  • "My one piece of advice to anyone who is on the pursuit of happiness is to know that you have a choice -- we can always choose to be happy. No, I am not talking about some saccharine, superficial ignoring of what is hurting attitude. In every situation we can decide how we regard the circumstances and our perspective then determines how we move forward or not." -- <a href="https://www.MarilynTam.com">Marilyn Tam</a>, author of <a href="http://www.amazon.com/Happiness-Choice-Five-Decisions-Where/dp/1118493168/ref=sr_1_1?s=books&ie=UTF8&qid=1361916910&sr=1-1&keywords=marilyn+tam">The Happiness Choice: The Five Decisions That Will Take You From Where You Are to Where You Want to Be</a>

  • "Happiness, or fulfillment, comes when we step outside ourselves and serve. Short term happiness comes from chasing “stuff” -- food, drugs, material items, realtionships, etc. But we all know that doesn’t last. Contribution, service, connection and love -- when we learn how to cultivate these things within ourselves and then give them away to others in whatever form inspires us most, we have stepped into a larger world. If you are seeking joy, realize that joy is service. No matter what the economy, government or other people are doing, there is always an opportunity to serve others. When we realize this and act on it, happiness is sure to follow." -- <a href="https://twitter.com/MastinKipp">Mastin Kipp</a>, CEO/Founder of <a href="https://twitter.com/TheDailyLove">@TheDailyLove</a>.

  • "If we want happiness, I think we should follow classic Greek wisdom and live with <em>areté</em>. The word directly translates as 'excellence' or 'virtue,' but has a deeper meaning -- something closer to 'expressing the highest version of ourselves.' When we're showing up fully moment to moment, there's no room for regret/anxiety/disillusionment, just a whole lot of happiness. Here's to getting our <em>areté</em> on!" -- <a href="https://twitter.com/_Brian_Johnson">Brian Johnson</a>, CEO of <a href="http://www.entheos.com/">en*theos</a>

  • "Let's see: When it comes to seeking happiness, the kiss of death is feeling <em>entitled</em> to happiness or believing that some other person is essential for you to be happy. People need to lower the bar in terms of what brings them happiness in life. Never tell yourself that you are an extraordinary person, as that will ensure your unhappiness. Rather, discover how liberating being ordinary is and begin your journey to happiness with your feet firmly planted on the ground." - <a href="https://twitter.com/CarolineMyss">Caroline Myss</a>, author of <a href="http://www.amazon.com/Anatomy-Spirit-Seven-Stages-Healing/dp/0609800140/ref=la_B000APAWW6_1_2?ie=UTF8&qid=1361918540&sr=1-2">Anatomy of the Spirit: The Seven Stages of Power and Healing</a>

  • "Happiness comes through finding peace and freedom within ourselves and bringing happiness to others." -- <a href="https://twitter.com/MatthieuRicard">Matthieu Ricard</a>, author of <a href="http://www.amazon.com/Happiness-Guide-Developing-Lifes-Important/dp/0316167258/ref=la_B001IO9SGO_1_1?ie=UTF8&qid=1361981079&sr=1-1">Happiness: A Guide to Developing Life's Most Important Skill</a>

  • "Realize that we are in charge of our inner emotions. We control how we feel from the inside out and we can decide how we respond to what goes on around us. Once we realize we are at the control desk of our inner world, then the responsibility is with us to steer our emotions. We can choose happiness -- wherever we are on the journey of life. Positive emotions breed increased health, wellbeing and success. The happier we allow ourselves to feel, the more we create positive outcomes. Happiness is a choice. That's the secret." -- <a href="https://twitter.com/susie_pearl">Susie Pearl</a>, author of <a href="http://www.amazon.com/Instructions-Happiness-Success-Step---Step/dp/1440556288/ref=sr_1_1?s=books&ie=UTF8&qid=1361918048&sr=1-1&keywords=instructions+for+happiness">Instructions for Happiness and Success</a>

  • Arianna Huffington How To De-Stress With the GPS For the Soul App

    Arianna Huffington: How To De-Stress with the GPS for the Soul App Download the App: http://www.huffingtonpost.com/2013/02...

"Many of the articles written in response to the bombing have quoted individual tweets reflecting qualitative micro-stories," said Dr Danforth.

"Our instrument reflects a kind of quantitative macro-story, one that journalists can use to bring big data into an article attempting to characterise the public response to the incident."

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 of the scale and the saddest at the bottom.

Averaging the volunteers' responses, the scientists assigned an overall score to each word. The word "happy" itself scored 8.30, "hahaha" 7.94, "cherry" 7.04 and the more neutral "pancake" 6.96. The words "and" and "the" scored a truly neutral 5.22 and 4.98.

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At the bottom of the scale, the word "crash" scored 2.60, "war" 1.80 and "jail" 1.76.

Trending words such as "explosion", "victims" and "kill" pushed the hedonometer down to its lowest ever level on April 15.

Positively scored words such as "prayers" and "families" also spiked that day - but not for positive reasons.

"If we remove 'prayers', 'love', and 'families' it's not going to change the day's overall deviation from the background because of all the other words," said Dr Danforth.

Currently the hedonometer is updated every 24 hours, but further development could see billions of words collected daily to provide a minute-by-minute barometer of global happiness.

The team is also trying to expand beyond "atoms" of single words to "molecules" of two-word expressions.

"It's the relative context that is so important, which is why the sudden drop from the Boston Marathon bombings jumps out at you," said Brian Tivnan, a hedonometer researcher from the MITRE Corporation, a US big-data not-for-profit organisation. "The hedonometer shows the pulse of a society."

The scientists acknowledge that happiness is a slippery word that means different things to different people.

"We're not trying to tell you that contentment is better than happiness - we're not trying to define the word," said Dr Danforth. "We're just saying we're measuring something important and interesting. And, now, sharing it with the world."

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.

Also on HuffPost:

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  • Write Down What You're Grateful For

    Write down three new things you are <a href="http://www.psychologytoday.com/basics/gratitude" target="_hplink">grateful</a> for each day into a blank word document or into the free app<a href="http://itunes.apple.com/us/app/ijournal-notebook-journal/id426811138?mt=8" target="_hplink"> iJournal</a>. Research shows this will significantly improve your <a href="http://www.psychologytoday.com/basics/optimism" target="_hplink">optimism</a> even six months later, and raises your success rates significantly.

  • Focus On The Positive

    Write for two minutes a day describing one positive experience you had over the past 24 hours. This is a strategy to help transform you from a task-based thinker, to a meaning based thinker who scans the world for meaning instead of endless to-dos. This dramatically increases work happiness.

  • Exercise

    Exercise for 10 minutes a day. This trains your brain to believe your behavior matters, which causes a cascade of success throughout the rest of the day.

  • Meditate

    <a href="http://www.psychologytoday.com/basics/meditation" target="_hplink">Meditate</a> for two minutes, focusing on your breath going in and out. This will help you undo the negative effects of multitasking. Research shows you get multiple tasks done faster if you do them one at a time. It also decreases <a href="http://www.psychologytoday.com/basics/stress" target="_hplink">stress</a> and raises happiness.

  • Send A Positive Email

    Write one, quick email first thing in the morning thanking or praising a member on your <a href="http://www.psychologytoday.com/basics/teamwork" target="_hplink">team</a>. This significantly increases your feeling of social support, which in my study at Harvard was the largest predictor of happiness for the students.