The 20 happiest nations in the World are:

1. Denmark 
2. Switzerland 
3. Austria 
4. Iceland 
5. The Bahamas 
6. Finland 
7. Sweden 
8. Bhutan 
9. Brunei 
10. Canada 
11. Ireland 
12. Luxembourg 
13. Costa Rica 
14. Malta 
15. The Netherlands 
16. Antigua and Barbuda 
17. Malaysia 
18. New Zealand 
19. Norway 
20. The Seychelles 
Other notable results include:

23. USA 
35. Germany 
41. UK 
62. France 
82. China 
90. Japan 
125. India 
167. Russia
The three least happy countries were:

176. Democratic Republic of the Congo 
177. Zimbabwe 
178. Burundi


From Science Daily 2006