The city of Vienna boasts the best living standard in the world for the third straight year, followed by Zurich and Auckland, while at the bottom, Baghdad has the lowest quality of living, according to the Mercer 2011 Quality of Living Survey released Tuesday by Mercer, a U.S-based leading global provider of consulting, outsourcing and investment services.

Mercer ranked a total of 221 cities for their overall quality of living and for personal safety, based on 39 factors grouped in the following ten categories: political and social environment, economic environment, socio-cultural environment, health and sanitation, school and education, public services and transportation, recreation, consumer goods, housing and natural environment. It made the survey with an aim to help governments and multi-nationals compensate their employees fairly when placing them on international assignments.

The survey shows that European cities represent over half of the cities in the top 25. Cities in Australia, New Zealand and Canada also performed well on the list. Singapore is the highest-ranked Asian city, taking the 25th spot. China's Hong Kong SAR, which took the 70th spot in the list, ranked 3rd among the Asian cities, and was the top dog of Chinese cities.

The cities with the lowest quality of living include Khartoum, Sudan (217), Port-au-Prince, Haiti (218), N'Djamena, Chad (219), Bangui, Central African Republic (220), and Baghdad, Iraq (221).

Following are the top 25 cities with the highest quality of living in the world:

  Singapore, Singapore