Puerto Vallarta, Jalisco, Mexico - The World Happiness Report 2016 Update, which ranks 156 countries by their happiness levels, was released last week in Rome in advance of UN World Happiness Day, which was celebrated on March 20th.

A landmark survey of the state of global happiness carried out by the United Nation's Sustainable Development Solutions Network, World Happiness Reports are based on the analysis of data gathered from surveys of thousands of people who were asked to grade their lives on a scale of zero to 10. The first report was published in 2012, the second in 2013, and the third in 2015.

The reports review the state of happiness in the world today and show how the new science of happiness explains personal and national variations in happiness. They reflect a new worldwide demand for more attention to happiness as a criteria for government policy.

In the 2016 World Happiness Report Update, Denmark was ranked the world's happiest country, and the east African nation of Burundi, plagued by political unrest, was listed as the most distressed of the 156 countries rated.

The Update found that countries with lower levels of inequality tend to be happiest overall, with Switzerland, Iceland, Norway and Finland completing the top five.

Here are the Top 25 World's Happiest Countries for 2016:

1. Denmark
2. Switzerland
3. Iceland
4. Norway
5. Finland
6. Canada
7. Netherlands
8. New Zealand
9. Australia
10. Sweden
11. Israel
12. Austria
13. United States
14. Costa Rica
15. Puerto Rico
16. Germany
17. Brazil
18. Belgium
19. Ireland
20. Luxembourg
21. Mexico
22. Singapore
23. United Kingdom
24. Chile
25. Panama

The report also found people were happier in countries where there was less inequality of happiness, which have reportedly increased globally over the past decade.

Report author Jeffrey Sachs, director of the Earth Institute at Columbia University, said measuring self-reported happiness "should be on every nation's agenda."

"Rather than taking a narrow approach focused solely on economic growth, we should promote societies that are prosperous, just, and environmentally sustainable," he added.