Togo, Burundi, Syria, Benin and Rwanda were least happy.
Switzerland is the happiest place on Earth, thanks to its healthy GDP and the high life expectancy rates, among other things.
Switzerland ranks No. 1 on the United Nations' list of the world's happiness countries. The country succeeds Denmark , which has held the title since the survey's inception in 2012. Iceland , Denmark, Norway and Canada round out the top five, while the U.S. comes in at No. 15, according to World Happiness Report.
Togo, Burundi, Syria, Benin and Rwanda were least happy, the report said.
The 10 top countries are all small or medium-size Western industrial countries with average life evaluations of 7.4 on the 0 to 10 scale.
Released on Thursday, the report is based on data from the Gallup World Poll and takes into account six variables: social support, freedom, generosity, corruption, health problems and household income.
"Happiness is increasingly considered a proper measure of social progress and a goal of public policy," the report said. "[A]n increasing number of national and local governments to use happiness data and research in their search for policies that could enable people to live better lives."