Is it possible to measure the happiness of the world's population? Remarkably it is, and the first World Happiness Report published today does just that.

Even more remarkable is next Monday's United Nations conference on happiness, for which the report was prepared. Last July the UN General Assembly invited all member governments to give more importance to happiness as a goal of public policy and mandated this conference as part of the process.

This means that there is now high world-level support for the demand that governments pay more attention to the happiness of their peoples when they form their policies. This is not, we emphasize, a matter of following the whims, fads, and consumer urges of the population. These do not, according to the evidence, lead to happiness. It is, rather, a matter of helping societies to find a path to what really matters more deeply and lastingly for well-being.

So what does matter in determining the happiness or life satisfaction in a nation? Income of course matters to everyone, especially the poorest. As the report shows, the richest countries are a lot happier than the poorest. The four happiest are all in Northern Europe (Denmark, Norway, Finland and the Netherlands) and the four least happy are in Sub-Saharan Africa. On a 0-10 scale, the average life evaluation score is 7.6 in the first four countries and only 3.4 in the last four.

But income is only one among many factors that explain the variation in happiness among people. As the report describes, income explains only about one-twentieth of the variation within nations that can be explained statistically, and across countries it explains about one-eighth of the explained variation. The other factors besides income can be divided into those that are mainly social and those that are mainly personal.

Countries differ hugely in the strength of their networks of social support ("If you were in trouble do you have relatives or friends you can count on to help you whenever you need them?"). They also differ in the degree of corruption in government and business, and of course in personal freedom and security. All these factors matter a great deal. So too does the state of the labor market. High and stable employment is extremely important. Therein lies the case for active labor market policies, job training, and various innovations in working hours flexibility.

Turning to more personal factors, a crucial one is mental health. A person's mental health many years earlier is a better predictor of his current happiness than his current level of income. Policy-makers need to take note. Mental illness comprises more than 40 percent of disability in advanced countries, according to the World Health Organization. Yet even in rich countries, it is estimated that only around one-fourth of the mentally ill are in treatment.

Physical health is also a major factor affecting happiness. It has to be a major priority in poor countries, and in rich countries for people in retirement.

Not surprisingly, individual values are also important. People who care more about other people are also themselves on average happier. Other things equal, people who single-mindedly chase higher incomes are less happy. And psychologists and neuroscientists can now show that training in altruism increases a person's happiness.

So there is every reason to be hopeful. We can now measure happiness in ways that provide genuine information and that are even identifiably correlated with objective measurements in the brain through various kinds of imaging. Psychologists, philosophers, economists, neuroscientists, sociologists, and each of us in our own internal reflection already know a lot about what causes lasting happiness. The next step is to get this knowledge more widely used by governments and by individuals, and there are movements like Action for Happiness that try to promote this. The pioneering Kingdom of Bhutan, which is leading the way with the concept of Gross National Happiness in place of Gross National Income, provides an outstanding example, and is the leading nation in stimulating this week's UN Conference. The OECD, which brings together the world's high-income countries, and many national governments in addition to Bhutan, have also begun to reorient their thinking towards a more serious measurement of happiness as an additional guide to public policy.

Over the last 40 years, sadly, measured happiness has not increased in the United States despite sharply rising incomes. The problems of poverty, insecurity, corruption, loss of social trust, and other factors are weighing heavily on America's sense of well-being. But there are also many countries where happiness has increased markedly. If the world applies the growing body of knowledge on happiness and well-being, we can surely help to build a world with much more happiness and a lot less misery.

The World Happiness Report is edited by the authors and is available here. The report provides the evidence and sources for all of the above remarks.

John Helliwell, of the Economics Department of the University of British Columbia, co-directs the 'Social Interactions, Identity and Well-being' program of the Canadian Institute for Advanced Research.

Richard Layard is the Director of the Wellbeing Programme at the London School of Economics' Centre for Economic Performance, and author of the book Happiness - Lessons from a New Science.