Vienna retains the top spot as the city with the worlds best quality of living, according to an international study.The Austrian capital comes first for a second year in a row in the 2010 edition of Mercers Quality of Living Survey.The Swiss cities of Zurich and Geneva follow in second and third place, while Vancouver in Canada and Auckland, New Zealand, come in joint fourth.Mercer Austria boss Josef Papousek said of Viennas triumph: “This result is mainly down to the citys high safety level, the stable political circumstances and its functioning infrastructure.”Mercers rankings are based on a point-scoring index, which sees Vienna score 108.6 exactly the same figure it achieved in 2009. Iraqi capital Baghdad comes bottom of the list featuring 221 cities with just 14.7 points. Cities are ranked against New York as the base city which has been given an index score of 100.Europe has 16 cities amongst the worlds top 25 cities for quality of living. Dusseldorf is the best German city in sixth place, while the lowest-ranking Western European cities are Leipzig in Germany, and the Greek capital Athens.London is the highest-ranking city of the United Kingdom in 39th place, followed by Aberdeen, Scotland, in 53rd place.Slagin Parakatil, Senior Researcher at Mercer, said the group also identified cities with the best eco-ranking this year. The extra index is based on water availability and drinkability, waste removal, quality of sewage systems, air pollution and traffic congestion.Canadian city Calgary is at the top of this index followed by Honolulu, capital of the US state of Hawaii. Vienna only reached 44th place in this category.British magazine The Economist rated Vienna as the second most-liveable city in the world after Vancouver, Canada, last year.These results might boost the Social Democrats (SPÖ) campaign as Vienna residents head to the polling booths in autumn. Pollsters said the party, which has an absolute majority in the city parliament, might suffer losses.A poll conducted by Vienna University and the city government presented in 2009 showed that 69 per cent of Viennese are “happy” or “very happy” to live in the city. Pollsters spoke to 8,700 city residents between May and December 2008.