I have just come back from 11 weeks overseas, including a couple of weeks in two of the world's most densely populated places - New York and Mexico City.

The thing that strikes you is how many well-attended events are taking place every day and night across many neighbourhoods in these mega cities, especially in Manhattan, the throbbing heart of New York.

The thing that strikes you coming back is how suburban, quiet and unexciting even Australia's largest cities are.

I believe the reason they are so devoid of cultural life is directly related to the fact they have been allowed to sprawl so far and wide.

After coming back from my trip, I tried to recapture some of the exhilaration of staying in New York and moved into a rental flat in the Sydney suburb of Darlinghurst.

It's a great place, and one of the very few areas that matches the pace of life you can enjoy across much of New York, and the easy access to museums, art galleries, music and restaurants.

For those not familiar with Sydney, Darlinghurst sits snugly between the City and Paddington, Kings Cross and Surry Hills - some of Sydney's most cosmopolitan and urban areas.

It is in the City of Sydney council area, which neighbours Sydney's most densely populated local government area, Waverley.

The City of Sydney itself would probably take the title of the most densely populated area, except that a vast swathe of it is populated by office workers, not residents.

ABS figures from 2005 show Waverley managed a population density of 6,647 people per square kilometre, while other areas in and around the Sydney CBD have densities between 5,000 and 6,000.

Sound impressive? Think again.

According to Demographia figures from 2000, even the more suburban area of Queens in New York had a population density of 7,897 people per square kilometre, while Manhattan had an astonishing density of 26,978.

Generally low-rise inner-London managed to fit 8,980 people into each square kilometre according to the UK's statistical agency in its 2002 figures.

The difference between Australia's cities and overseas urban centres becomes even greater when you look beyond the inner-city areas, as Australia's cities sprawl much further than almost anywhere else.

On Demographia's 2010 estimates, Sydney ranked 681st in the world for population density against other urban areas with populations over 500,000.

Sydney's overall population density was 2,000 people per square kilometre, and that is excluding commuter areas such as Richmond, the Central Coast and Blue Mountains, which have far lower densities.

Sydney was ranked by Demographia as Australia's most densely populated city ahead of Melbourne (1,600 people per square kilometre), Adelaide (1,400), Perth (1,200), Canberra (1,100), Hobart (1,000) and Brisbane and Darwin (900).

Brisbane and Darwin came in with lower densities than many Australian regional centres, including Coffs Harbour and Shepparton.

In fact, there are significant problems comparing international population densities, depending on where you draw the boundaries of what is considered part of the urban area.

For instance, for its international comparison, Demographia includes several cities outside New York as part of the urban area (along with the land in-between) pulling its density below Sydney's at 1,800, but crediting it with an enormous land area of 11,264 square kilometres (around six times bigger than Sydney).

Any of you who have been to New York would know that it isn't really six times the size of Sydney, and if you measured Sydney's land area comparably you'd have to include all the space to Wollongong in the south, Katoomba in the west and at least the Central Coast in the north.

In contrast, New York City and its boroughs have a much smaller area of 782 square kilometres and a density of 10,238.

Cultural cost

There are many people who no doubt think it's great that Australia's cities are so geographically large for their population sizes - it means access to backyards for many, and parks, bushland and other public open spaces for all.

There's also an undeniable fact that the vast bulk of the world's most densely populated cities are in the developing world, where millions crowd without any personal space in gigantic slums - an illustration of what happens when poverty drives urban density too high.

But there are many trade-offs for Australia's extreme low-density lifestyle.

We all know about the lengthy commutes for those who live in the suburbs or satellite cities, and the pollution from those who've abandoned inadequate public transport systems to drive.

Not to mention that the inadequacy of those transport systems is caused largely by the cost of reaching so few people over such a large distance, meaning that the huge infrastructure investments required could never be substantially recovered through fares, which are already heavily subsidised.

However there's also a less talked-about cultural trade-off caused by having so many people so far away from the centre of the city that still houses the bulk of its museums, galleries, theatres, music venues and (to a lesser extent) restaurants.

Whereas in Manhattan there's almost certainly a cultural, and definitely a culinary institution of some sort on the block you live on, or at least within five minutes walk, in Australian cities many people are not only forced to commute hours for work, but then face extra hours of travel to go out.

When I say go out, I'm not just talking concerts and parties, I'm also talking about taking your kids to a museum or a show.

Perhaps it's no coincidence that America is the home of 'mall rat' culture, with Australia following suit, as countries with some of the least dense cities in the world (the boroughs of New York aside where, unlike most of the rest of America, you don't find too many malls).

Particularly for the young who can't drive, it's just too hard for many to get into the urban centre on weekends, leaving people dispersed in suburban cinemas and shopping complexes, or stuck at home in front of the television or computer.

For older people, the problem becomes one of finding the incredible amounts of money it takes to buy or rent even a small apartment anywhere within a 10 kilometre radius of the city centre if you want regular, easy access to the cultural benefits of the inner-city.

The problem may get even worse in New South Wales if the new State Government carries through on its promise to shift Sydney's planning guidelines from building 70 per cent of homes as infill in existing areas and 30 per cent in uninhabited greenfield sites, to a ratio of 50-50.

One can't really demolish all the sprawl that's been allowed to occur on Sydney's west, north-west and south-west fringes, but one can consolidate it and stop it spreading further as the population keeps increasing.

This was the idea behind a 70-30 per cent mix - building the majority of new homes in areas where people already live, where shops and cultural institutions are already established, and where (at least in some cases) there's existing public transport.

Urban infill means that an increasing number of areas in Sydney can reach the density required to sustain street shopping, cafes and restaurants, cultural institutions and entertainment venues.

It means an increasing number of people will be able to afford to make the choice to live near the inner-city and enjoy its amenity.

Alternatively, a return to increased rates of urban sprawl will do nothing to assist the economic and cultural growth of existing areas in Sydney, and instead grow the number of isolated people living with poor infrastructure and nothing to do outside their home.

NIMBY threat

For society as a whole it's a no-brainer to build on what you've got before tearing up more farms and bushland for new homes in areas relatively few people want to live, except out of necessity.

However, far too many people are solely interested in protecting the lifestyles they acquired cheaply years ago, before population pressures sent the outer suburbs 50 kilometres or more from the city's centre.

While it is admirable to protect the historic heritage of one's city, as occurred in the green bans that saved vestiges of Sydney's colonial Rocks district, it's often self-interest in one's own amenity or one's property value that prevents or slows development across much of Sydney's inner-urban areas, as it no doubt does in other Australian cities.

The economics is simple.

The more homes that get built in inner-urban areas, the greater the supply on the market, the lower the property appreciation of existing owners - a fact consciously or instinctively appreciated by many of those current residents responsible for electing their local governments, and maintaining slow and conservative development approval practices.

Potential future residents simply don't get a say at the local level, necessitating state government intervention.

The lack of density in Sydney's existing urban areas also goes against developer arguments that its a lack of greenfield land release that is causing high urban property prices.

Given an affordable choice, most people simply don't want to live that far away from work, friends, family and infrastructure.

Many young Australians are ready for a shift away from the big three or four-bedroom family home in the suburbs to an apartment lifestyle - certainly in the early years of their home-owning life at least.

Home price growth over recent years illustrates this trend: while houses have traditionally outperformed apartments in price growth, over the past five years the trend has shifted, with unit prices rising 7.3 per cent while detached houses rose 7 per cent, according to figures from RP Data.

The out-performance in price comes despite apartments forming an increasingly large share of the market: RP Data notes that medium and high-density homes now account for 35 per cent of capital city sales, as opposed to only 25 per cent 15 years ago.

In the four most expensive capital city markets (as at August last year) of Sydney, Melbourne, Canberra and Darwin, units accounted for around 40 per cent of monthly property sales, as houses in accessible locations became unaffordable for most buyers.

RP Data expects the trend towards medium and high-density housing to continue.

John McGrath, the CEO of McGrath Real Estate, wrote in an article last year that the demand for apartments was coming from two directions: older people who wanted to downsize (often to a more desirable location), and young couples who were increasingly raising at least their first child in an apartment due to lifestyle, location preferences and affordability.

He also noted that there is a stronger rental demand for apartments than houses, "because more of them are close to transport, cafes and shops".

This indicates the real supply shortage - affordable apartments near Australia's city centres.

While the unique character of some parts of inner-city areas needs to be protected and maintained, there also needs to be other areas that are turned over to a higher density of development, to give people the choice to live in a vibrant, populated, commute-free environment - a choice that many Australians want to make, but the bulk of people can no longer afford.

Michael Janda is the ABC's online business reporter