Denmark is the happiest nation, according to new World Values Survey data.

Puerto Rico and Colombia joined Denmark at the top of the list along with Ireland, Switzerland, the Netherlands, Canada and Sweden.

In the survey, researchers measured happiness in 97 nations, almost 90 percent of the world's population, by simply asking people how happy they were, and how satisfied they were with their lives as a whole.

The response rate was high -- 97 percent -- with respondents giving answers that strongly correlated with how satisfied they were with various aspects of life such as gender equality and tolerance of minorities.

Also, countries whose respondents reported high levels of happiness were much more likely to be democracies than were countries that were ranked lower.

But many countries are growing in happiness. A separate survey, funded by the National Science Foundation, was completed by researchers at the University of Michigan's Institute for Social Research in Ann Arbor and showed increased happiness from 1981 to 2007 in 45 of 52 other countries.

Researchers said in a news release that the overall rise in reported happiness is due to greater economic growth, democratization and social tolerance.

United States' Happiness

The United States remained at No. 16 in the World Values Survey, the relatively same position found in the 2000 survey.

The fairly high placement contrasts with the public's dissatisfaction with U.S affairs.

According to an April 2008 New York Times/CBS News public opinion poll, around 81 percent of Americans said they believed the country is on the "wrong track," which was the most negative response in the past 25 years.

Ronald Inglehart, a political scientist at the university and director of the study, said although the results seem contradictory, there is an explanation.

"Though by no means the happiest country in the world, from a global perspective, the U.S. looks pretty good," Inglehart said in the news release. "The country is not only prosperous; it ranks relatively high in gender equality, tolerance of ethnic and social diversity and has high levels of political freedom."

Money Influences Happiness

Although there are many influencing factors, researchers noted that wealth is important for happiness.

"The relative importance of economic prosperity to happiness changes as societies get richer," Inglehart said. "In low-income countries, one's economic situation has a huge impact on happiness. But among more prosperous countries, political freedom and social tolerance play a greater role in determining how happy people are."

Three of the world's poorer countries with long histories of repressive government -- Moldova, Armenia and Zimbabwe --are at the bottom of the happiness list.

The World Values Survey has measured happiness since 1981. Its researchers have interviewed more than 350,000 people.