Denmark won the title three of the four times the report has been issued, losing to Switzerland only once.
People in Burundi are the least satisfied with their lives, according to the survey of 156 countries, but residents of Benin (153rd place), Afghanistan (154), Togo (155) and Syria (156) aren't doing much better.
The United States ranked 13th in overall happiness, lagging behind Canada (6), the Netherlands (7), New Zealand (8), Australia (9), Sweden (10), Israel (11) and Austria (12). Germany came in 16th place, while other superpowers -- the United Kingdom (23), Japan (53), Russia (56) and China (83) -- were markedly lower.
Some countries that saw drops suffered economic and political turmoil -- including Greece, Italy and Spain -- while Ukraine's political trouble and violence likely caused a significant drop in happiness there.
Measuring happiness is important
Happiness is a better measure of human welfare than measuring education, health, poverty, income and good government separately, the report's editors argue.
There are at least seven key ingredients of happiness: People who live in the happiest countries have longer life expectancies, have more social support, have more freedom to make life choices, have lower perceptions of corruption, experience more generosity, experience less inequality of happiness and have a higher gross domestic product per capita, the report shows.
"Measuring self-reported happiness and achieving well-being should be on every nation's agenda as they begin to pursue the Sustainable Development Goals," said Jeffrey Sachs, the report's co-editor and director of the Earth Institute at Columbia University, in a statement.
"Indeed the goals themselves embody the very idea that human well-being should be nurtured through a holistic approach that combines economic, social and environmental objectives," Sachs said. "Rather than taking a narrow approach focused solely on economic growth,we should promote societies that are prosperous, just, and environmentally sustainable."
Not just about the money
Iceland and Ireland both suffered through banking crises that dramatically affected their economies but didn't greatly affect their happiness, according to the report. What both countries have is a high degree of social support, enough to put Iceland in third place and Ireland in 19th place this year, according to the report.
Strictly focusing on financial well-being can obscure the larger picture, according to the University of British Columbia's John Helliwell.
"In Norway, it's quite common for people to paint each other's houses even though they can all afford to pay to have their houses painted," said Helliwell, a report co-editor and co-director of the Canadian Institute for Advanced Research.
"They go out of their way to help each other, and it becomes a social event, and those events are enormously supportive of well-being," Helliwell said. "In the commercialization of activity -- when people are more likely to buy things than to do them for themselves and each other -- we lose something along the way."
Inequality of happiness
It turns out that people are also happier in countries where there's less inequality of well-being, the report found. And happiness inequality has increased significantly "in most countries and regions of the world," said Helliwell, comparing 2012-15 data with 2005-11 data.
The country of Bhutan, a tiny country famous for measuring the "Gross National Happiness" of its people, ranked No. 1 in happiness equality, followed by Comoros and the Netherlands. South Sudan, Sierra Leone and Liberia had the highest happiness inequality.
A country may have really rich and really poor people, and the poor people don't have enough money to construct a good life for themselves, he said. Or people may have money but have no social support or friends, or live in an area where there's government corruption or lack of freedom to make their own life choices.
The birth of 'Gross National Happiness'
It's no surprise that Bhutan would come out on top, despite not being a world economic power: Its Prime Minister proposed a World Happiness Day to the United Nations in 2011 and launched this international focus on happiness.
Following in Bhutan's footsteps, the U.N. General Assembly declared March 20 as World Happiness Day in 2012
, recognizing "happiness and well-being as universal goals and aspirations in the lives of human beings around the world."
In recent years, other countries have made happiness a public policy goal of their governments. Bhutan, Ecuador and the United Arab Emirates and Venezuela have all appointed "Minsters of Happiness" to focus on the happiness of their people.