Auckland has been ranked the third-best city for quality of living in a recent global survey.

The City of Sails has kept its third placing in the Quality of Living survey by recruitment consultancy Mercer for the fifth year, having also achieved the podium position in 2012, 2015, 2016 and last year.

The survey ranks 450 cities throughout the world, considering 39 factors within 10 categories; consumer goods, economic environment, housing, medical and health considerations, natural environment, political and social environment, public services and transport, recreation, schools and education, and socio-cultural environment.

Austria's capital, Vienna, ranked highest for the ninth year in a row, followed by Zurich in Switzerland, and then Auckland.

Wellington was the country's next highest-ranking city, placing in 15th, while Sydney was Australia's top-ranked city at 10th, followed closely by Melbourne at 16th place.

Mercer NZ chief executive Martin Lewington said New Zealand remains an attractive destination for expatriates on assignment.

"There are a number of factors which have contributed to companies looking at establishing headquarters or relocating expats to Auckland," he said.

"NZ's natural environment and subtropical climate, stable political and social environment and good medical and health services are the top three contributing factors for Auckland retaining third spot in the global rankings."

This year, Mercer provided a separate ranking on city sanitation, which analyses cities' waste removal and sewage infrastructure, levels of infectious disease, air pollution, water availability and quality.

Auckland ranked fifth and Wellington sixth for city sanitation, with Honolulu taking first place, followed by Helsinki and Ottawa in joint second.

"Having clean air and water that is safe to drink is a significant consideration for many expats, even more so if there are young children involved," Lewington said.

"With Auckland and Wellington's air and water quality being among the world's cleanest, compared to some other popular expat destinations, it means that NZ becomes more attractive for global talent."

Mercer's survey is one of the world's most comprehensive and is conducted annually to enable multinational companies and other organisations to compensate employees fairly when placing them on international assignments.

Mercer also helps municipalities to assess factors that can improve their quality of living rankings.