Australia is the tenth happiest country in the world but new data shows a major age-gap in well-being. 

The annual World Happiness report, conducted in partnership with the UN, Gallup World Polls and the Oxford Wellbeing Research Centre, features experts using responses from people in more than 140 nations to rank the world's 'happiest' countries. 

Respondents are asked to evaluate their life satisfaction over the past three years on a scale of one to 10. 

The happiness ranking for under 30s in Australia is 19, while it jumps back up to nine for over 60s. 

The report shows young people are struggling in many regions of the world, excluding Europe. 

"For the US, Canada, Australia and New Zealand, happiness has decreased in all age groups, but especially for the young, so much so that the young are now, in 2021-2023, the least happy age group," the report wrote. 

It is the first time the report gives separate rankings by age group. 

Lithuania tops the list for children and young people under 30. 

For people over 60, Denmark is the happiest place to be. 

“We found some pretty striking results," said the editor of the World Happiness Report, professor John Helliwell.

"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.”

Findings also suggest that the wellbeing of 15- to 24-year-olds has fallen in Western Europe, the Middle East and North Africa, and South Asia since 2019. 

Another surprise for researchers was the fall in rankings for the US to 23 and Germany to 24.

It's the first time the US has dropped out of the top 20, which can also be explained by the disparities in age group rankings. 

Happiness in the US is ranked 62 for under 30s and 10 for over 60s.

Millennials and younger age groups in North America were also significantly more likely than older age groups to report loneliness.

Finland has topped the overall list for the seventh successive year, followed by Denmark, Iceland, Sweden and Israel.

Jennifer De Paola, a happiness researcher at the University of Helsinki, told AFP that Finns' close connection to nature and healthy work-life balance were key contributors to their life satisfaction.

Researchers take into account factors such as life expectancy, GDP, having someone to count on, a sense of freedom, generosity and perceptions of corruptions. 

These factors explain the differences across nations but the rankings themselves are based only on the answer people give when asked to rate their own lives. 

Afghanistan is the least happy country. 

The top 10 countries have remained largely the same since the COVID pandemic but in the next 10, it shows Eastern European countries such as Czechia, Lithuania and Slovenia are rising in happiness. 

“Effective policymaking relies on solid data, yet there remains a significant lack of it in various parts of the world," said the CEO of Gallup, Jon Clifton.

"Today’s World Happiness Report attempts to bridge some of these gaps by offering insights into people’s perceptions of life on Earth. It offers more than just national rankings; it provides analytics and advice for evidence-based planning and policymaking.

"Our role in research on world happiness is a natural fit with our longstanding mission: providing leaders with the right information about what people say makes life worthwhile.”