Credit: Olivier Morin/AFP/Getty Images

Known for its stunning fjords, cozy ice hotels, and Viking history, Norway edged out Denmark as the happiest country in the world, according to the World Happiness Index.

Northern Europe dominated the top-ranked countries, with Norway being followed by Denmark, Iceland, Switzerland, and Finland.

The index is a global scientific study that has been conducted since 2012, and this edition looked at polling data collected from 2014 to 2016. While the polling has only been taking place since 2012, the researchers looked at data going back further in time to have a better sense of changing attitudes.

Economic researchers used six factors to determine a country's happiness ranking: GDP per capita, healthy years of life expectancy, a sense of having social support through family or friends, trust in government, a feeling of general personal freedom, and generosity as measured by recent donations to charity.

The United States dropped in its ranking, falling behind Israel and sinking to number 14 on the list. This dip took place despite average incomes and healthy life expectancy having increased in the U.S. in the past ten years. The authors attributed the dip to a decrease of social and personal freedoms as well as an increase in perceived corruption.

“It's the human things that matter. If the riches make it harder to have frequent and trustworthy relationship between people, is it worth it?” John Helliwell, the lead author of the report and an economist at the University of British Columbia in Canada, told the Associated Press. “The material can stand in the way of the human.”

Poverty as well as corruption contributed greatly to the low happiness of some of the countries that ranked at the bottom of the list. The Central African Republic came in last, and Burundi second to last.

“The chapter defines misery as being below a cutoff value for life satisfaction, and shows by how much the fraction of the population in misery would be reduced if it were possible to eliminate poverty,” reads an excerpt from a chapter on the key factors determining happiness and unhappiness.