A Fairfax Media analysis of Tax Office data released on Wednesday has revealed a significant re-ordering of Sydney's top 10 richest postcodes over the past decade.

Three of Sydney's traditional enclaves of high income earners - Palm Beach, Kirribilli and Killara - have disappeared altogether from the list.

They have been replaced by three newcomers: Double Bay, Paddington and Balmain.

The prime ministerial postcode of 2027 - which includes Point Piper and Darling Point - has retained its position as home to the highest average taxable incomes in the country at $189,293 - up 32 per cent over the decades.

But hot on Point Piper's heels is neighbouring Vaucluse at $185,684 (up a whopping 57 per cent) and Bellevue Hill at $163,820 (up 41 per cent).

These two eastern suburbs postcodes have knocked Hunters Hill and Northbridge from their positions a decade ago as second and third highest.

Mosman retains its place as Sydney's fourth richest postcode, at least according to what we tell the Tax Office each year.

Eastern suburbs postcodes now take out six of the top 10 richest postcodes, and the north just four - an exact reversal of the situation a decade ago.

Driving the shift from north to east are two deep trends of ageing and rising inequality, according to Bill Randolph, the director of the City Futures Research Centre at the University of NSW.

"The ultra-rich are becoming much more concentrated," Dr Randolph said.

"It's people at the top end who have done remarkably well. They will congregate together. They don't like to spread themselves across the city."

The appeal of the eastern suburbs was clear: "It's well located. It's got the views. It's become the place to live. It's got the social cachet. The north shore perhaps doesn't have that cachet anymore."

A higher concentration of retirees declaring lower incomes was also likely a major driver of slower income growth on the north shore, Dr Randolph said.

"Maybe they're better at minimising their tax on the north shore. More sensibly, it is probably an ageing thing."

The figures rank postcodes by average taxable income - that is, total income declared to the Tax Office, minus tax deductions like negative gearing and work related expenses. They compare the latest data available for 2014-15 with 2004-05.

Across Australia, surgeons enjoy the highest average taxable incomes of $377,044. It also pays, on average, to be an anaesthetist ($341,041), a financial dealer ($235,444), a psychiatrist ($204,236) and a judge or other legal professional ($191,201).

Dr Randolph warned increasing income polarisation across Sydney between could have harmful effects on the local economy.

"It leads to an unbalanced city. Lower income workers need to live somewhere. They're all out in the suburbs, but they have got jobs in the eastern suburbs, as cleaners, care attendants or shop assistants."

"There is general agreement that socially imbalanced cities are probably increasingly unproductive ones."

"I don't think we're there yet. But we're heading that way."