Sydney is the epicentre of a "crisis of suburbia", as new figures reveal inner city postcodes enjoyed the fastest income gains over the past decade, while the poorer outer suburbs went backwards after inflation.

Experts have warned of a "ghettoisation" of the harbour city, as divergent job opportunities, rising inner city house prices and crumbling urban infrastructure increasingly trap Sydneysiders in silos.

An analysis by Fairfax Media of Tax Office income data has revealed residents of Sydney's richest postcode, Point Piper, now enjoy average incomes five times that of Auburn residents, up from 3.5 times a decade ago.

Despite the recent focus on Mt Druitt, it is Auburn which emerges as the postcode with the lowest average individual taxable income in 2012-13, at $36,186. Mt Druitt comes in at 15th. Lakemba, Campsie, Cabramatta, Fairfield and Punchbowl help fill out the top 10 poorest postcodes list. Residents of all these areas actually went backwards over the decade, with income growth below a rise in consumer prices of 31 per cent.

At the other end, the postcode of Point Piper and Darling Point in Sydney's eastern suburbs reported the highest average individual taxable income, at $177,514.

Astonishingly, it also enjoyed the fastest growth rate of all 229 postcodes studied – an astonishing 61 per cent.

The director of the City Futures Research Centre at UNSW, Bill Randolph, said the figures were evidence of the "suburbanisation of disadvantage" in Australian cities.

Sydney, in particular, was undergoing a "great urban inversion" whereby the inner city slums of the last century were revitalised by better job opportunities, while and great suburban spread of the post World War II era became the new home of disadvantage.

"In effect, the old crisis of the inner city has been substituted by a new crisis of suburbia," Professor Randolph told Fairfax Media.

"The centrifugal forces that spread employment and housing outwards away from city centres during the 20th century have been replaced by a centripetal force pulling economic activity and housing investment back into the centre," he said.

Sydney appeared to be experiencing a "ghettoisation" effect, an associate professor at the Melbourne Institute of Applied Economic and Social Research, Roger Wilkins, said.

"Sydney is notorious for being a bit more segregated by postcode than some other cities, like Melbourne."

Joblessness in the Blacktown area now stands at 7.2 per cent, compared to just 3.6 per cent in Sydney's Eastern suburbs.

"Since the downturn, unemployment rates of low skilled people have fallen whereas the higher skilled people tend to be better at retaining employment," Professor Wilkins said. "It's not just about what wage rates people are getting, it's that there are fewer people with jobs."

The global financial crisis marked a turning point for Sydney's low income suburban postcodes.

"Before 2009, it was really the story of a rising tide lifting all boats, just lifting some a bit more than others. Now we are seeing more and more people going backwards, particularly at low incomes and even the middle income level."

And it will be an even harder road ahead, Professor Wilkins warned.

"We had this historically unprecedented growth in household incomes. We won't see it again in our lifetimes, unfortunately."

with Conrad Walters