Finland tops an index of the happiest nations in which to live.

The World Happiness Report published Wednesday ranked 156 countries by their happiness levels, based on factors such as life expectancy, social support and corruption.

This year's report is the first to include immigrants, who were evaluated in 117 of the countries.

The Nordic nations, none particularly diverse, have dominated the index since it first was produced in 2012. In topping the index, Finland nudged neighboring Norway into second place.

Rounding out the Top 10 are Denmark, Iceland, Switzerland, Netherlands, Canada, New Zealand, Sweden and Australia.

The United States fell to 18th place from 14th last year in the index done by the U.N. Sustainable Development Solutions Network.