In times like these, no one is immune to depression. But surveys show the Danes are the happiest people in the world, and a core factor is a quality in global short supply -- trust.

From Erasmus University's World Database of Happiness to a World Values Survey from the University of Michigan in late June, the 5.5 million people in the Scandinavian state have ranked top of most happiness surveys for the last 20 years.

As economists probe better ways to measure well-being than pure wealth, they say the Danes -- who are also among the world's most prosperous people -- have a tradition of equality and trust that is not widely replicated.

Perhaps one concrete example of the benefit of this trust can be seen in Denmark's stock exchange.

It has not escaped global carnage -- it is down around 37 percent so far this year -- but over five years it is the top performer among developed markets measured by MSCI Indexes, with a gain of around 13 percent putting it just ahead of oil-rich Norway.

OECD economist Justina Fischer -- a German who has studied subjective well-being and its societal and economic correlations for many years -- puts Denmark's happiness down to the fact that people consume a relatively equal share of the wealth they generate, and trust each other.

"Denmark is one of the countries with the highest level of trust among people," she told Reuters. In other countries, people are more cynical about institutions from government to business, as well as each other.

Denmark was one of the first countries in the current market turmoil to promise an unlimited guarantee on deposits and senior debt in banks.

"Trust in peers -- also institutional trust -- but especially trust in peers is a significant and decisive determinant of your subjective well-being," Fischer said.

Recruiter Soren Christiansen, 32, relaxing with his girlfriend in their up-market rented apartment in one of Copenhagen's newly built residential areas, said trust creates a safer everyday life for him.

"It makes me happy to live in a country where you can walk safely around and you do not have to be afraid," he said.

The problem for Denmark's government is that not enough people outside know either how happy the Danes are, or why. So the government is spending $75 million to improve its image.

Danish diplomat Klavs Holm said this branding project was being prepared before a Danish newspaper in 2005 published cartoons of the prophet Mohammed, earning Denmark sharp protest among Muslims: it is not targeted at the Muslim world.

He said most people picture Denmark in terms of Hans Christian Andersen, The Little Mermaid and Tivoli Gardens. What they don't see is the country's "unique Danish values".

"The Danes are 'The Happy People'. Why?" said the Under-Secretary for Public Diplomacy, citing how Danes are comfortable with simple pleasures like swimming in the harbour on a summer's day, which could be deemed too risky elsewhere.

"A woman is riding her bike with two kids in a box in front -- and it is even raining -- how can she do that? The Danes are devoted to biking and to fighting global warming locally. Those are some of the values that interest other people," he said.

One woman cycling through Copenhagen, decorator Mette Ellevang Petersen, 26, said it meant a lot to her to feel safe and that she could rely on other people.

Although she is a nervous about her future job situation -- decorators are often first to suffer in a slowdown -- she said she mostly felt sorry for the people around the world who have suffered the consequences of the crisis.

The Danish island of Samso, whose inhabitants have after a decade achieved a target of self-sufficiency in renewable power, is one example of a self-reliant community initiative that Denmark has to offer.

Exactly how the Danes became so trusting of each other is not clear, but it may have been inherited through generations, said professor and self-styled happiness researcher Christian Bjornskov at the University of Aarhus.

"We believe that the origin of this trust can be traced far back. Possibly back to some Viking norms," Bjornskov told Reuters, adding these assumptions were speculative.

As an indication, he said surveys have shown that the descendants of those Scandinavians who emigrated to the United States in the 19th century generally are the most trustful Americans today.

The OECD's Fischer noted that economists have found a positive correlation between trust and economic growth.

"If you trust someone in a market transaction you have lower transaction costs. You do not even have to have a contract because you trust his or her words. So you have no contract costs, you have no enforcement cost."

Bjornskov said Danish trust is very clearly connected with a better economy and a better competitive position.

"It means that the judicial system functions better in Denmark, education works better than in a lot of other countries. The trust contributes to the happiness, but it also contributes to concrete economic results," he said.

Fischer cited a new interest in making social indicators -- such as happiness or subjective well-being -- acceptable to politicians as a complement to traditional GDP.

"The GDP indicator is very much a quantitative measure of well-being and we have to add a quality dimension to that," she said.

The OECD has since 2007 been working with other international bodies to encourage development of statistical data that goes beyond conventional economic measures to measure societal well-being.

In the wake of the crisis, Bjornskov has said, Danes will have sadder lives. But in newspaper Berlingske Tidende he forecast they would hold their global top slot, and should be feeling firmly on top of the world by 2010.