Burundi has been rated the world's least happy country to live in. Nine other sub-Saharan African countries, along with Syria, Afghanistan and Yemen, made up the rest of the bottom 13.

Aiming to "survey the scientific underpinnings of measuring and understanding subjective well-being," the report, now in its fourth edition, uses six components to rank 157 countries by happiness levels. They are: per capita gross domestic product (GDP), healthy years of life expectancy, social support as measured by having someone to count on in times of trouble, trust as measured by perceived absence of corruption in government and business, perceived freedom to make life decisions, and generosity as measured by recent donations.

"A report like this is a message not only to poor countries... (there are) even some inexpensive ways to do better," said Professor Jeffrey Sachs, head of the SDSN and special advisor to the UN Secretary General Ban Ki-moon.

"Focus on health, focus on improving the honesty of government, doesn't cost a lot of money and it can be done. It's a message to rich countries also like the United States that have a kind of pure money mentality and have let the social fabric fall apart," he said.

The top 13 this year were Denmark, Switzerland, Iceland, Norway, Finland, Canada, Netherlands, New Zealand, Australia, Sweden, Israel, Austria and the US.