According to a recent Wall Street Journal/NBC poll, only 18 per cent of registered voters believe he has performed poorly.

"What the Bloomberg reign most profoundly demonstrated is the power of an extremely wealthy man who is beholden to no special interests," according to magazine. "Bloomberg effectively created his own special interests and used the government to turn a city into a data-driven, health-conscious image ... of himself."

Bloomberg loves reeling off statistics as testament to his success: the lowest murder rate in 50 years; at 52 million, a record number of tourists; life expectancy up by 2.5 years in the last 12 years. Violent crime, the great scourge of New York until the 1990s, continues to drop.

Bloomberg's aggressive public health policies, such as banning smoking in bars and restaurants, have contributed to a 50 per cent decline in teen smoking.

But there is another, less savoury record: a homeless population of 50,900 - 21,300 of them children.

Bloomberg's move to change the law and lift the two-term limit for mayors, was unpopular. He won only a narrow victory in 2009 despite an expensive campaign.

Others complain that Bloomberg overstepped the line between protecting public health and personal choice. A judge blocked his attempts to ban super-sized sugary soft drinks on health grounds.

His vast wealth - Bloomberg pilots a helicopter and flies by private jet to a second home in Bermuda on weekends - has painted him as divorced from reality.

ranks him the 13th richest person on the planet and the 29th most powerful, just one place below the Indian prime minister, leader of the world's biggest democracy.

Bloomberg's future remains unclear. His philanthropy is legendary and he has held up former US president Bill Clinton and Microsoft founder Bill Gates as examples of good work he would still like to do.

But in the short term, he is planning his first holiday with his girlfriend in 12 years - to play golf in Hawaii and New Zealand.