Despite residents' constant groaning over traffic jams and overcrowded hospitals and schools, Vietnam is considered the second happiest country in the world, behind Costa Rica, with Colombia third.

The ranking, the Happy Planet Index, was compiled and released by the New Economics Foundation, a UK independent think tank.

The Happy Planet Index ranks countries based on the health and happiness they produce per unit of environmental input, using global data on life expectancy, happiness and environmental sustainability.

Accordingly, Costa Rica , Vietnam and Colombia live the longest, happiest, most sustainable lives.

The ranking this year marks a rise for Vietnam compared to previous years. It ranked 12th and 5th in 2006 and in 2009, respectively.

Besides Vietnam , the rest of the countries in the top 10 are from South America, including Belize , El Salvador , Jamaica , Panama , Nicaragua , Venezuela , and Guatemala .

The US ranks 105th and the UK ranks 41 on the index.

The lowest-ranked countries are Qatar , Chad and Botswana .

The independent think tank aims to improve quality of life by promoting innovative solutions to economic, environmental and social issues.-VNA