A new report finds people in the United States are not very happy compared to the rest of the world.

The U.S. has dropped to number 23 on the World Happiness Report released in conjunction with the UN's International Day of Happiness. It was the first time the country was out of the top 20 since the report was first published in 2012.

The findings are powered by data from the Gallup World Poll and analyzed by some of the world's leading well-being scientists.

The lower U.S. ranking was driven by a large drop in the well-being of Americans under 30.

Experts used responses from people in more than 140 nations to rank the world's 'happiest' countries. Finland tops the overall list for the seventh successive year.

Afghanistan remains bottom of the overall rankings as the world's 'unhappiest' nation.

The top countries no longer include any of the largest countries. In the top ten countries, only the Netherlands and Australia have populations over 15 million. In the whole of the top 20, only Canada and the United Kingdom have populations of over 30 million.

For the first time, the report gives separate rankings by age group, in many cases varying widely from the overall rankings. The report found that those born before 1965 are, on average, happier than those born since 1980.

Among Millennials, evaluation of one's own life drops with each year of age, while among Boomers life satisfaction increases with age.

Rankings are based on a three-year average of each population's average assessment of their quality of life. 

Prof John F. Helliwell, founding Editor of the World Happiness Report, said, "We found some pretty striking results. There is a great variety among countries in the relative happiness of the younger, older, and in-between populations. Hence the global happiness rankings are quite different for the young and the old, to an extent that has changed a lot over the last dozen years."

Researchers found that, globally, young people aged 15 to 24 report higher life satisfaction than older adults, but this gap is narrowing in Europe and recently reversed in North America.

Findings also suggest that the well-being of 15- to 24-year-olds has fallen in North America, Western Europe, the Middle East and North Africa, and South Asia since 2019 - but in the rest of world, it has risen. 

Prof Jan-Emmanuel De Neve, an Editor of the World Happiness Report, said, "We documented disconcerting drops, especially in North America and Western Europe. To think that, in some parts of the world, children are already experiencing the equivalent of a mid-life crisis demands immediate policy action."