Finland is the world's happiest country, according to an annual survey issued on Wednesday that put Burundi at the bottom of the happiness index and found Americans were getting less happy even as their country became richer.
The UN Sustainable Development Solutions Network's (SDSN) 2018 World Happiness Report ranked 156 countries according to their scores for things such as GDP per capita, social support, healthy life expectancy, social freedom, generosity and absence of corruption.
Finland, rose from fifth place last year to oust Norway from the top spot. The 2018 top-5, as ever dominated by the Nordics, is: Finland, Norway, Denmark, Iceland, and Switzerland.
The United States came in at 18th, down from 14th place last year. Britain was 19th and the United Arab Emirates 20th.
One chapter of the 170-page report is dedicated to emerging health problems such as obesity, depression and the opioid crisis, particularly in the United States where the prevalence of all three has grown faster than in most other countries.
While income per capita has increased markedly in the United States over the last half century, the happiness index has been hit by weakened social support networks, a rise in perception of corruption in government and business and declining confidence in public institutions.
"We obviously have a social crisis in the United States: more inequality, less trust, less confidence in government," the head of the SDSN, Professor Jeffrey Sachs of New York's Columbia University, told Reuters.
For the first time since it was started in 2012, the report, which uses a variety of polling organisations, official figures and research methods, ranked the happiness of foreign-born immigrants in 117 countries.
Finland took top honours in that category too, giving the country a statistical double-gold status. The foreign-born were least happy in Syria, which has been mired in civil war for seven years.
"The most striking finding of the report is the remarkable consistency between the happiness of immigrants and the locally born," said Professor John Helliwell of Canada's University of British Columbia.
"Although immigrants come from countries with very different levels of happiness, their reported life evaluations converge towards those of other residents in their new countries," he said.
"Those who move to happier countries gain, while those who move to less happy countries lose."
Top 5 happiest countries
Top 5 least-happy countries
Central African Republic 中非共和国
South Sudan 南苏丹