On Sunday there was a good panel discussion on Radio NZ talking about density and the Unitary Plan without the usual scaremongering from the likes of Auckland 2040. It’s well worth a listen if you have a spare 20 minutes.
Urban density marks a shift away from a traditional single-storey home on a section, towards multi-storey apartment and townhouse developments. Proponents say increasing urban density is important for a booming city like Auckland, while others argue against this type of housing and its impact on communities. Wallace is joined by RNZ Auckland Correspondent Todd Niall, Auckland’s deputy mayor Penny Hulse, and Bill McKay, senior lecturer at the School of Architecture, Auckland University.
or listen here
Since first talked about back in 2013, the Unitary Plan has been like a roller-coaster ride. There’s been the hope and anticipation for a better future for Auckland as the cart climbs a steep hill followed by that brief micro second of confusion before you realise you’re falling as groups opposing housing pipped up and were egged on further by one sided reporting from the Herald. Then came the twists and turns of the debate before that feeling of weightlessness as you go through a loop waiting for the councillors to make a decision. After catching your breath for a second there was then the smaller and less intense second stage as the process was repeated. Then just as you thought the ride might be coming to an end it throws a few last unexpected twists and turns at you. And that’s where are now, right in the middle of latest saga the Unitary Plan has seen.
The current issue stems back to December when the council released its evidence and updated residential zonings as part of the hearing process. I wrote at the time.
As part of the hearings process the council are allowed to make a final submission in response to the issues raised by the public. They say they are currently confirming their position on a range of topics and one of those is zoning. Taking into account a range of factors, the council is suggesting some changes to the zones in the plan that determine what can be built where. It’s these changes which have had the Herald and a number of councillors worked up. The factors include
- the submissions and evidence
- the interim guidance on some topics from the hearings panel – such as on viewshafts and heritage controls
- further analysis of the zones i.e. fixing inconsistencies
- amended infrastructure plans such as the addition of light rail on the isthmus
This doesn’t mean that the Unitary plan is being changed just that the council are saying that based on the evidence and updated information they think some changes should be made. The independent panel hearing the Unitary Plan could rejected them outright or go completely the other way and say they don’t go far enough then recommend significant increases.
Overall the changes weren’t all that much. Those that did move generally only changed by a small amount and combined 78% of all residential areas were still limited to two storeys while a further 17% was limited to three storeys.
The Herald through Bernard Orsman along with groups opposing housing have even gone the absurd level of calling three storeys ‘high-rise’. One of the funny things of it all is that in suburbs where most of the opposition originates the size and scale of buildings that the opposition groups oppose are quite prevalent, just as single houses which they seem quite happy with.
According to those opposing the Unitary Plan, these are high-rise and shouldn’t be allowed.
What’s changed recently is following a meeting in Kohimarama – and I suspect a lot of lobbying of councillors over the summer break – supposedly a majority of councillors want to withdraw the councils evidence.
Auckland Council’s proposal to rezone thousands of homes for more intensive housing and apartments has lost the support of a majority of councillors, with councillor Sir John Walker today speaking out against the changes.
“If the mayor wants my vote we are going to have to come to a compromise,” said Sir John, who did not spell out what that solution would be.
“I’m on the residents’ side. I don’t want to see high rise buildings towering over Auckland.
“I don’t trust the town planners. They present one thing and change their mind and do another,” said the Olympic gold medallist.
Sir John said he supported calls to withdraw the changes, which see large swathes of suburban Auckland rezoned for multi-storey buildings, terraced housing and apartments in the council’s latest submission to the Unitary Plan.
Under the “out of scope” changes to zoning, meaning no residents asked for them in the proposed Unitary Plan, there is no formal right of reply for affected property owners.
Sir John’s position means 11 of the 21 councillors want the council to withdraw the out of scope changes from the Unitary Plan process.
The other 10 are Cameron Brewer, Cathy Casey, Chris Fletcher, Denise Krum, Mike Lee, Dick Quax, Sharon Stewart, Wayne Walker, John Watson and George Wood.
It seems that there’s also a degree of personal preference clouding decision making with Sir John also saying
Eight years ago he sold up and moved to a lifestyle block in Bombay “where you can’t build a single house”.
Sir John said the city should stick with low rise housing.
Why ruin the city with three-storey apartments? They might not be very high but I wouldn’t want to live next door to one
Now the majority claimed by Orsman is just on paper and the council haven’t actually formally voted to withdraw their evidence. We’ve also seen Orsman claim a lot of times in the past that the Unitary Plan was in the balance only to be easily passed by the council when they actually voted. To withdraw their own evidence would be incredibly stupid in my view as it would remove them from debate leaving it just up to what others had submitted and there were a lot of submissions calling for much more development to be allowed.
There were some very good responses to all of this yesterday which are worth covering.
Todd Niall at Radio NZ wrote this excellent piece pointing out that the Unitary Plan is a blueprint for the next 30 years and that the council need to take account all of those who will be living here in 30 years, not just those making the most noise now.
The debate and political anxiety comes as the deliberations near the end – the 30-year development blueprint for Auckland, the Unitary Plan, is due to be finalised by September.
It will eventually reshape much of Auckland’s residential landscape, with more of it looking increasingly city-like and less suburban – more multi-level and less like any other New Zealand city.
The heightened discussion poses a challenge for Auckland councillors. Should they heed the cries of the loudest of their constituents, or the ambitions of the quietest?
In short, who should have the dominant voice in shaping the future Auckland ?
The Herald got in on the act in its editorial.
It is too easy to panic politicians in election year, particularly in local body elections where the turnouts are usually low. It is easy to fill a public hall on local issues that are close to people’s homes and may affect their property values, and it is easy for individual politicians to be persuaded that a packed hall represents a popular uprising.
Plenty of us live next door to a double storey house without concern. But one more storey has the citizens in revolt, or so too many council members fear.
Let’s acknowledge the courage of those who are willing to defend the revised Unitary Plan and see it through. It may be easy enough for the mayor who is not seeking re-election, but not easy for Deputy Mayor Penny Hulse or council members Arthur Anae, Bill Cashmore, Linda Cooper, Chris Darby, Alf Filipaina and Calum Penrose. They have kept their nerve and put the city’s housing needs before their electoral safety.
If only they’d taken this stance all along we probably wouldn’t be in the mess we are right now. Alas I suspect we’ll back to business as usual with scaremonger articles soon.
The Property Council which is a lobby group for developers held no punches in it’s press release over the issue. Good on them.
Property Council is appalled with Auckland councillors who have withdrawn their support to rezone Auckland suburbs with the capacity for more housing and apartments.
Auckland Branch President Phil Eaton says soaring house prices are creating systemic social injustice, inequity and major economic risk.
“Let’s be absolutely clear about this. The councillors who have withdrawn their support to rezone and upzone suburbs to allow for more houses have done so at the expense of Aucklanders, because they want to come back after the local elections.
“Now, Baby Boomers have essentially locked an entire generation out of their own homes. Young people and families will never be able to work and live in Auckland, and ‘Generation Rent’ is the
legacy these councillors will leave behind.
“Local politicians must ditch their “Not in My Election Year” mentality and do what is right by all Aucklanders, not just some.”
Scaremongering by local politicians has residents believing their suburbs will be covered in high-rise apartments, when realistically less than 6% of suburbs will have apartments with more than three storeys: up just 1% from the previous version of the PAUP.
So where does that leave us. Councillor George Wood posted this the other day showing a briefing on Thursday.
We’ll be waiting to see what happens following Thursday. This is one roller-coaster I’d be happy not to ride again.
I have been pondering a comment in William Fischel’s generally excellent new book on zoning to the effect that:
…suburbanization and reduced urban density are worldwide phenomena. All but 16 of the 120 urban areas on every continent grew outward and reduced their overall population densities in the last decade of the previous millennium, even as almost all of them grew in total population.
This is an interesting claim, but one that I find very difficult to reconcile with the evidence on other “big picture” changes observed in cities over the last three decades.
In recent decades, agglomeration economies have gotten stronger and the structure of advanced urban economies has changed. This has in turn increased the premium that people place on proximity and centrality – a phenomenon well illustrated by Grimes and Liang (2007), who show how close proximity to the city centre shifted from being a “disamenity” to an “amenity” during the 1990s:
Relatedly, regulations limiting density are increasingly binding (and, in places like Auckland, San Francisco and New York, more costly than regulations limiting sprawl). This was nicely illustrated by three recent pieces of research that showed that (a) Auckland’s legacy planning regulations imposed twice as many costs on apartments as standalone houses, and that (b) the cost of legacy councils’ building height limits were higher than the cost of the city’s former urban growth boundary:
So colour me perplexed. On the one hand, I have a very respected and knowledgeable economist telling me that cities are getting less dense. On the other hand, I have a mass of evidence, often compiled by other respected and knowledgeable economists, that suggests that densities should be increasing, not decreasing.
As it turns out, Fischel’s claim is what my mathematician friends describe as “true but trivial”. It’s not inaccurate, but it doesn’t tell you anything interesting about the world either. The idea that urban densities are getting lower is in fact a statistical artefact – i.e. it’s a “fact” that arises from the way that Fischel has calculated population densities.
Calculating population densities is a slightly arcane subject. Last year, I wrote a short paper that explored alternative measures and explained why we should prefer a population-weighted density measure to a simple average density:
The most common approach to measuring population density is simply to divide the total population of a city by the total land area of the city. As shown above, this approach will tend to underestimate the density of cities with large expanses of lightly populated exurban land. However, this approach is commonly used for international comparisons due to the fact that it relatively straightforward to calculate…
The population-weighted density measure was introduced by Barnes (2001) to correct for the weaknesses of the simple average density measure. This measure was recently used by the US Census Bureau to produce consistent and meaningful data on American cities (Wilson et al, 2012). As the example above suggests, it more accurately reflects the density at which the average city resident is living (Eidlin, 2010).
Population-weighted density is estimated by calculating the density of all individual neighbourhoods within a city, assigning each neighbourhood a weight equal to its share of the city’s total population, and summing up the weighted density of all neighbourhoods. In other words, if a dense inner-city neighbourhood has ten times as many people as an outlying suburban neighbourhood, the inner-city area would be weighted ten times as heavily as the suburban area.
In other words, average density measures the density of the average hectare of land in the city, even if hardly anyone lives there, while population-weighted density measures the density of the neighbourhood that the average citizen lives in. Average density is not, therefore, a very meaningful number if you want insight about how people are living in a city.
Moreover, it turns out that a city’s average density can be declining even though every part of the city is getting more dense! This sounds counterintuitive, so I’ve put together a simple model showing how it can happen.
You can download the model here in case you’re interested in playing with it. For simplicity, I’ve assumed a linear city that extends in one direction from a centre. (This readily generalises to a city that extends in multiple directions.) Population densities are highest near the centre and decline exponentially with distance. (The distance decay parameter I’ve used loosely approximates observed outcomes in big NZ/Aus cities.)
I’ve tested the impact of a 20% increase in the urban population. In the model, intensification accounts for around 60% of growth, meaning that all existing developed areas get ~12% denser. The remaining 40% of growth occurs in low-density greenfield areas, which expand the city’s footprint by 33%.
Mathematically-minded readers will see where this is going. But for the visual learners out there, here’s what it looks like on a graph:
Because the urban footprint has expanded by 33% while the population has only grown by 20%, the city’s average density has dropped by 10%. But if you look at the graph, you can see that it would be ridiculous to say that the city is spreading out and de-densifying. In fact, every part of the city is getting more dense, and most growth is occurring within built up areas.
In other words, Fischel is wrong to say that cities are getting less dense. Horizontal growth is certainly happening – but so is vertical growth.
I would argue that the latter trend – towards proximity, density, and efficient use of land – is the more significant of the two. We are currently seeing big changes in the function, structure, and use of cities. Recognising and responding to those changes is important, and policies that unwittingly stifle them will have large economic and social costs.
That’s why it’s important to measure density (and other urban phenomena) accurately – bad measures often contribute to bad policy decisions.
How do you think cities are growing?
Can cities fill up? Has Auckland simply become too populated to accommodate any more people, as some have argued? Do we need to put up the “closed” signs?
In a word, no. There is plenty of room to accommodate more people within the existing urban footprint, although doing so would require us to do things a bit differently. It wouldn’t mean losing the things that make Auckland special – but it could mean that we gain some new amenities.
Emily Badger over at Washington Post’s Wonkblog has put together some interesting graphics showing how cities almost always have the capacity to accommodate a few more people. She writes:
Echoes of a similar suspicion to the contrary, though, are widespread in how we talk about the places where we live. The entire city of San Francisco is “cooked. Done.” There’s no more room in Silicon Valley, either. Brooklyn is at capacity. Boston, too. The nicest parts of Northwest Washington long ago reached the limit. Chicago’s coveted Lincoln Park wants fewer people. Even whole countries now suffer from this condition: Britain just can’t take in any of those refugees because the island, at long last, is full.
Built into these arguments is a powerful but slippery contention: It is possible to fill up a place…
“Economists reject absolutes like ‘full’ and ‘need,'” says Joe Cortright, one of several urban economists I asked. “It’s always about tradeoffs and choices.”
Cities, in particular, are about tradeoffs between hectic streets and vibrant economies, between scarce parking and neighborhoods worth traveling to, between cramped subway cars and the mass of humanity that makes the subway possible.
And so, from an economist’s point of view, there is no such thing as a full place. Especially not in America, where our neighborhoods, as urban planning professor Sonia Hirt puts it, are “astonishingly low density” compared to the rest of the industrialized world. Maybe your particular geology can’t handle the foundation of a mile-high skyscraper. But, for the most part, we can always make choices to make more room, to build taller and denser, to upgrade schools and rethink roads to let more people in.
That we don’t isn’t a limitation of physics. It’s a matter of politics disguised as physics.
Here’s one of their graphics showing how much more intensely urban space is used in different places. (Side note: these figures are based on average density across the urban area, which can be misleading in some cases. Population-weighted density is a far better measure.) If you’re at the bottom end of this range – as Auckland is – it’s hard to argue that it’s physically impossible to build up a little bit.
However, points on a map don’t necessarily feel very real. So here’s another comparison between Auckland and San Francisco (via Mikavaa). As you can see, the Auckland isthmus is about the same size as the tip of the San Francisco peninsula:
We can see the difference between the two cities even in a satellite map. San Francisco’s urban footprint shows up as a swathe of white and grey, while Auckland’s is largely a mix of green and muddy grey. That’s not to say that San Francisco is all concrete jungle. It’s preserved extensive urban parks – the Presidio, Mount Tamalpais, Ocean Beach, McLaren Park, Golden Gate Park, etc – and reclaimed much of its waterfront for people. But its parks, unlike Auckland’s are situated within a densely-developed, productive, high-amenity urban fabric.
A comparison with San Francisco, a city with similar geographic constraints to Auckland, shows how inefficiently our limited space is used. The tip of the San Francisco peninsula houses around 1 million people. The Auckland isthmus accommodates less than 400,000 people. (The San Francisco figures include San Francisco City, Daly City, and South San Francisco; the Auckland figures include the Waitemata, Albert-Eden, Puketapapa, Orakei, and Maungakiekie-Tamaki local boards.)
Although San Francisco is over twice as densely populated as the Auckland isthmus, it isn’t exactly compromising on aesthetics or amenity. The city is widely appreciated for its beautiful natural settings, which are enhanced by appropriate infrastructure:
It’s also known for its historic buildings and beautiful neighbourhoods. Here’s an example of a fairly typical form for a San Francisco neighbourhood – lots of timber-framed midrise buildings close together:
And lastly, San Francisco’s always had a vibrant and innovative culture, both in the arts and in the booming tech industry. In other words, the city’s density has supported, not undermined, its natural surroundings, built environment, economic productivity, and cultural vibrancy. Of course, the city’s got some challenges – such as high housing costs resulting from limits to further intensification – but they are largely a consequence of its success as a dense place with high amenity and high productivity.
But overall, what this comparison shows is that Auckland has the potential to use its limited land area far more efficiently – without compromising our natural or urban environments.
Growth: what is it good for?
Accommodating a growing population can certainly be challenging. It means having to find more money to invest in transport and water infrastructure to enable new residents to live and travel in the city. As Auckland Council’s recent consultation on the Long Term Plan shows, asking people to pay more is never a very popular proposition – even if they like how the money’s being spent.
And, as Stu pointed out in his post on Auckland house prices this Monday, population growth can also put pressure on housing markets. Multiple research papers from the Reserve Bank have shown that increases in net migration tend to be followed by increases in house prices – shown in this chart. Obviously, homeowners do quite well out of this, but others face added costs:
In short, it’s not surprising that some people feel trepidatious about population growth and migration. And it’s not surprising that those anxieties are especially present in Auckland, which is projected to continue growing rapidly over the next three decades.
While unease about population growth is understandable, I’d argue that it’s misplaced. In my view, the benefits of urban population growth in New Zealand far outweigh the costs. While large urban areas can become dysfunctional – think of Beijing’s astonishing smog problems or the high cost of infrastructure in sprawling American cities – New Zealand’s cities are nowhere near large enough for the diseconomies of scale to triumph over the economies of scale.
This is easy to see if we look at the periods when Auckland hasn’t been attracting migrants. Here’s a chart from a presentation on Auckland’s demographics by Auckland Council social researcher Alison Reid. It displays the composition of Auckland’s population growth since 1922. In recent decades, natural population increase – i.e. people having babies – has been the biggest source of growth. Net migration is important, but it can be quite volatile – surging up and then crashing back.
What stood out to me from this chart was that the years with little or no net migration to Auckland have not been good times for the city. Net migration slowed to a trickle during the Great Depression, and turned negative during the constrained years during and after World War Two. More recently, quite a few people fled Auckland during the economically calamitous Muldoon years. Net migration remained low during the painful adjustments imposed by the following two governments.
I wasn’t living in Auckland during the 1990s – my parents had joined the queues leaving via Auckland airport – but friends who were say that the city was turning into a ghost-town. History shows that shutting off the migration tap has never led to a better, more vibrant city or more opportunity for residents. It’s simply been a sign of failure.
My hypothesis is that New Zealand has a strong feedback loop between net migration and economic growth. When growth prospects get worse – as they did in the 1970 and 1980s – it dissuades people from coming here and encourages Kiwis to leave for greener pastures. This in turn worsens growth prospects by sucking consumer demand out of the economy and reducing perceived household wealth (i.e. lowering house prices).
By contrast, good growth prospects tend to attract migrants to New Zealand’s cities and encourage potential emigrants to stay. This in turn leads to a virtuous cycle between higher growth and increased migration.
We can’t fully control this process, as it depends in part on what’s happening in Australia and the rest of the world (not to mention macroeconomic variables that we don’t fully understand). But we can make sure that our cities are in a good position to take advantage of population growth.
The first, and most important thing we can do is to build better cities that are able to attract and efficiently accommodate more people. In Auckland, for example, we’ve got some challenges, including transport investment that’s been heavily skewed towards cars (and only cars) and rising house prices. But the flip-side of those is that we’ve got great opportunities to:
- Improve transport choice by investing in Auckland’s “missing modes” – a frequent bus network throughout the city, rapid transit infrastructure, and safe walking and cycling infrastructure
- Improve housing choice by providing opportunities for people to develop higher-density residential typologies in market-attractive areas
- Invest in great public spaces, such as Auckland’s waterfront and increasing numbers of shared spaces.
Second, as we attract more people to our cities, we need to accommodate them in an efficient and environmentally responsible way. This means enabling people to live in areas that are accessible to jobs, shops, and other amenities. As I found when I looked at carbon emissions from commutes in New Zealand cities, people in inner-city areas are considerably more environmentally friendly than their co-workers from the urban fringe.
Moreover, the data shows that increasing density can be a positive-sum game for existing communities as well as for the environment. At the city level, we can’t observe any relationship between rising population densities and congestion – fears of traffic-choked streets just don’t seem to have materialised in practice. (So much for diseconomies of scale!)
On the other side of the ledger, suburbs with higher population densities have better consumption choices. Many of the services that people rely upon – from vege shops to Japanese restaurants to public transport to roads – exhibit strong economies of scale, which means that they get better when there are more people around.
Which suggests that there is also a third important thing that we need to do, which is to tell good stories about the opportunities that urban growth will offer us. New Zealand’s used to thinking of itself as a rural economy with some cities sprinkled around as afterthoughts. That’s a dated and inaccurate self-image when over half the economy is located in our three largest cities.
So, what’s your perspective on urban growth?
One of the many reasons that people choose to live in cities is that cities offer variety. As Stu Donovan has argued before, being around more people sometimes seems inconvenient, but it also exposes you to new ideas, new people, and new consumption choices.
I’ve previously written about the value that people place on choices in housing and transport markets, and how having more choices is particularly valuable for people on low incomes. This week, I want to look at how cities provide us with choice in the retail and restaurant markets.
My hypothesis is that there are economies of scale in the provision of both public and private goods. In more straightforward terms, that means that if you live closer to more people, you can have more public transport, more parks, more good restaurants, more shops, and so on and so forth. If this intuition is true, the best way to obtain variety at an affordable price is to live in a dense area of the city.
In order to test this hypothesis, I took a look at Statistics New Zealand’s Business Demography statistics, which provide information on the number of businesses (“geographic units”) and employment within particular industries. Very helpfully, Stats NZ publishes this data at a suburb level (“area units”, in Stats-speak).
I’ve focused on two particular types of businesses that serve households’ daily needs:
- ANZSIC industry H45, which includes restaurants, bars, and clubs
- ANZSIC industry G41, food retail, which includes supermarkets and other small-scale food retailers.
I mapped the density of these businesses throughout different Auckland suburbs. Blue colours show higher densities of restaurants/bars or food retailers; yellow colours show lower densities. A few clear patterns emerge. First, densities tend to be highest in inner city suburbs, and even more so in the city centre. Second, there are also pockets of higher density around satellite centres like Takapuna and New Lynn. Third, the density of retail and restaurants tends to be much lower on the fringe of the city.
How can we explain these patterns? Why are some areas so much better supplied with retail and dining options than others?
We can get some insights by looking at the built form retail and restaurants areas in different areas of the city.
Here’s what a retail street looks like in the city centre, where high residential and employment density sustain a lot of activity both day and night. This is O’Connell St before and after its shared space transformation. Notice how people are just walking up:
Here’s what retail looks like in an inner-city shopping and dining district, Ponsonby Road, which is surrounded by old suburbs of medium population density. It has lots of shops right on the street, plus a bit of parking tucked around the back:
And here’s what retail looks like in a newer suburb at the edge of town – Albany centre. It’s physically separated from nearby residential areas, highly car-dependent, and as a result, it requires large swathes of parking to support each shop or restaurant:
Albany Mall – Aucklands most modern Metropolitan Centre…
In other words, less parking is required to get shoppers to the door in densely populated areas – which should make it easier to sustain more shopping and dining options per square kilometre.
A simple econometric analysis seems to support this view. I attempted to explain the density of restaurants and food retailers in suburbs in terms of the population density and employment density of those areas. (Using Census and Business Demography data from Stats NZ.) As I hypothesised, there is a statistically significant, positive relationship between higher population and employment densities and the density of restaurants and food retailers. These two factors predict roughly 85% of the variation in restaurant and retail density in Auckland suburbs.
Regression results are reported in the table below, for anyone who’s interested. These aren’t perfect models – I suspect that it would be worth testing some spatial regression models, as retailers often attract customers from a wider catchment than a single suburb. Furthermore, we’d have to analyse changes over time in order to establish that increasing population density in an area will in turn increase retail diversity. But these results do provide a reasonable indication of the underlying relationships.
OLS regression models for restaurant and retail density
|Residual Std. Error (df = 339)
|F Statistic (df = 2; 339)
||*p<0.1; **p<0.05; ***p<0.01
What do these figures mean? The coefficients from the model – highlighted in bold – display the relationship (or “elasticity”) between population or employment density and density of restaurants or food retailers. They show that:
- Areas with 10% higher population density have, on average, 4.6% more restaurants/bars and 6.0% more food retailers (including supermarkets)
- Areas with 10% higher employment density have, on average, 6.2% more restaurants/bars and 4.9% more food retailers.
In short: Higher density can benefit people by giving them more choice in restaurant and retail markets. Having a mix of residential and commercial uses around is even better, as it can sustain activity throughout the entire day rather than just in the evenings or at lunchtime.
Stats NZ’s data isn’t granular enough to say, but I suspect that denser areas also have a greater diversity of dining and retail options. (This is intuitively obvious – if there are already two fish-and-chip shops in the neighbourhood, why would anyone choose to open up a third?)
What do you make of this data on density and retail choices?
Earlier this week, I took a look at the relationship between congestion and density. I was investigating geographer Phil McDermott’s claim, based on some dodgy data comparing between cities, that increasing density would increase congestion.
Economists know that it is difficult to make inferences about causality using cross-sectional analysis. Simply looking at variations between different cities doesn’t allow you to form robust conclusions about how those cities got to where they are.
One of the ways in which economists seek to strengthen their understanding of causality is to look at changes over time. For example, if you observe that increases in density tend to be followed by increases in congestion, then that is stronger (although not necessarily conclusive) evidence that there is a causal relationship.
With that in mind, it is worth asking: How have congestion and density changed in New Zealand cities over time? Unfortunately, we don’t have enough data points to conduct a robust econometric analysis, but we do have enough to start painting a picture of recent changes. We can draw upon two relevant sources:
I’m going to focus on NZ’s three largest cities – Auckland, Wellington, and Christchurch – as two of the three experienced big increases in density between 2001 and 2013. (MoT hasn’t collected data on Hamilton and Tauranga for as many years.) If these increases in density coincided with rising congestion, it may be an indication that intensification can lead to increased congestion.
Here’s the data. It shows that density has risen 33% in Auckland between the 2001 and 2013 Censuses, 17% in Wellington, and a mere 3% in Christchurch:
And here’s the Ministry of Transport’s Congestion Index, which measures the average minutes of delay per vehicle-kilometre, relative to totally free-flowing conditions. This is a bit of an unrealistic comparison, as a 2013 NZTA research report by Wallis and Lupton shows. The only way that you can totally avoid all queuing or stopping at traffic lights is if there are no other cars on the road. So it wouldn’t be realistic to say that we could speed up the average Auckland trip by half a minute per kilometre. However, this is still a useful indicator for changes from year to year.
While the Index bounces around a bit from year to year, the overall trends are clear. Levels of congestion are flat or falling in Auckland and Wellington, which experienced big increases in density over the last decade, and rising in Christchurch, which hasn’t gotten denser. In particular:
- Average delay for Auckland drivers was 25% lower in 2013 than it was in 2003
- Average delay for Wellington motorists fell 5% from 2004 to 2013
- Average delay for Christchurch drivers rose a staggering 31% between 2004 and 2010. Unfortunately, MoT’s monitoring seems to have been disrupted by the earthquake, but anecdotal evidence suggests that congestion has worsened since then.
In short, data on changes in density and congestion in New Zealand cities contradicts the notion that intensification will necessarily cause worse traffic congestion. If anything, it suggests that rising density may do the opposite, by making it more feasible for people to walk, cycle, or take public transport.
Do we need to treat this data with caution? Most certainly. As I noted earlier in the week, there are a number of omitted variables that influence congestion, such as such as changing consumer preferences, macroeconomic changes, and significant investments in both roads and public transport over the last decade. But it does suggest that wild claims about the negative traffic impacts of new apartment buildings should be taken with a significant grain of salt.
What do you make of this data?
A number of recent posts have taken a look at some of the “strategic misrepresentations” that people have used to argue for a sprawled-out, roads-focused Auckland. We’ve taken aim at some of the common fallacies, including:
A while back someone sent me an article by geographer Phil McDermott that really hits the trifecta of fallacies. He argues that building apartment buildings on arterial roads – precisely where they will have the best access to frequent public transport services on Auckland’s New Network – is a bad idea because it will lead to increased congestion on the roads.
McDermott’s argument is long on subjective judgments (young people may want apartments but old people downsizing from big suburban homes never will!) and short on quantitative analysis. Here’s his key piece of evidence that constructing apartments on arterial roads will inevitably lead to more congestion:
Congestion – the elephant in the apartment
That might be just as well because mindlessly boosting residential development on arterial roads promises simply to compound Auckland’s congestion problems.
We know higher densities are associated with higher congestion. Auckland’s geography means it already performs poorly on this count. The Tom Tom Congestion Index confirms this.
When the 2013 congestion index for 65 American and Australasian cities is plotted against population density (sourced from the Demographia website) Auckland sits among the worst performers – Vancouver, Sydney, Los Angeles, and San Francisco (Figure 2).
Figure 2: Population Density and Congestion
This is not a serious piece of analysis – it is an insult to econometricians. McDermott makes three elementary errors in this short excerpt alone.
First, he uses bad data that misrepresents levels of density and congestion in these cities. Matt has previously taken a look into the guts of the TomTom Traffic Index and found that it is not a useful measure:
It measures the difference in speed between free flow and congested periods. That means cities with lots of all day congestion there isn’t as much of a difference between peak and off peak times and therefore they get recorded as having less congestion.
Likewise, I’ve done some empirical work on population densities in New Zealand and Australian cities that has showed that Demographia’s statistics are similarly meaningless. Demographia measures the density of the average hectare of land in the city, rather than the density of the neighbourhood in which the average person lives. Nick has shown how badly these figures misrepresent the actual density of New Zealand cities:
Second, McDermott omits important variables and makes inappropriate inferences about causality. While he observes a correlation between two variables, that’s hardly sufficient to prove that building apartments will increase congestion. The causality could very easily run the other way. For example, it could be the case that the presence of congestion creates an incentive for people to live closer to employment and amenity. If that’s the case, then McDermott’s preferred policy of banning apartment developments would make Aucklanders much worse off by preventing them from minimising their travel costs.
Another possibility is that the relationship between density and congestion is mediated through other factors. Both may be caused by a third variable that McDermott has omitted, or there may be an intermediate step between density and congestion. (Or, as noted above, the measures themselves might be rubbish.)
A while back, CityLab’s Eric Dumbaugh provided an excellent illustration of the complex nature of congestion. He looks at data on US cities and finds that higher congestion is associated with higher, rather than lower, levels of productivity:
As per capita delay went up, so did GDP per capita. Every 10 percent increase in traffic delay per person was associated with a 3.4 percent increase in per capita GDP. For those interested in statistics, the relationship was significant at the 0.000 level, and the model had an R2 of 0.375. In layman’s terms, this was statistically-meaningful relationship.
Such a finding seems counterintuitive on its surface. How could being stuck in traffic lead people to be more productive? The relationship is almost certainly not causal. Instead, regional GDP and traffic congestion are tied to a common moderating variable – the presence of a vibrant, economically-productive city. And as city economies grow, so too does the demand for travel. People travel for work and meetings, for shopping and recreation. They produce and demand goods and services, which further increases travel demand. And when the streets become congested and driving inconvenient, people move to more accessible areas, rebuild at higher densities, travel shorter distances, and shift travel modes.
In light of these counterintuitive relationships, the simple two-variable OLS regression that McDermott is relying upon is almost certainly misleading.
Third, McDermott fails to recognise that people are less exposed to congestion in denser, mixed-use cities. It’s simple: when people have better transport choices – i.e. access to frequent bus services and rapid transit, and safe walking and cycling networks – it doesn’t matter as much that the roads are congested. Increasing Auckland’s density by constructing apartment blocks and terraced housing on arterial roads will make it easier for people to have those choices, because the arterial roads are where the frequent bus services under the New Network will go:
Frequency is freedom
Furthermore, density allows people to be closer to where they want to go. I find it odd that McDermott (and others) underestimate the importance of physical proximity in cities, even as people are paying high prices for the privilege. Building more homes in the areas that are accessible to jobs and amenities will allow more people to choose proximity over long commutes. (Without preventing others from making a different choice.)
A question for the readers: Would you rather have a 40 kilometre commute travelling at 80 km/hr, or a 5 kilometre commute moving at 30 km/hr? Show your work…
I thought a commenter on a recent post about a new apartment development on Great North Road had a really great point about the state of the debate:
…the fact is the intensifiers are not winning the argument, as was noted by someone else above. I wish they were but with the tin-ear people have here for this sort of argument, it doesn’t surprise me that it is being lost. Compare the nuanced arguments made here about transport (expansive, studied proposals like the CFN) to the “developers and freemarkets will sort it out” type arguments around intensification and you’ll see what I mean.
This rings true to me. Although I would argue that a lot of thought has gone into Transportblog’s analysis of policies like the Unitary Plan or the effects of limits on density, it’s often difficult to tell the good news stories about market-led intensification.
This is challenging in part because there appear to be trade-offs. Building an apartment building in Ponsonby is obviously a good thing for new residents, as they get to live in a nice area that they might not otherwise be able to afford. But it also has some disadvantages for existing residents, who may feel like they have to put up with more traffic, less sunlight on their porches, and so on and so forth.
In short, it’s easy to fall into an “us versus them” narrative – which is what I was arguing against in the earlier post. I don’t think this is necessary. There are many positive stories about rising residential densities and a lot of benefits for existing residents. We should start telling these stories.
Basically, it boils down to this:
If more people live in a neighbourhood, more services will be available locally for all residents.
Higher population densities make it more efficient for transport agencies to run high-frequency bus routes. They make it easier for supermarkets to open up in closer proximity, competing down prices for groceries. They make it easier for councils to justify improving local parks, improving streetlighting, and upgrading streets. Density allows there to be a cafe or two on every block, so residents can easily step out for a hot drink in the morning. This is all good stuff!
Essentially, having more people around you means that there’s a bigger local market for all sorts of useful things. As densities increase, neighbourhoods will become more convenient for the people who live in them. But if they don’t, there’s never going to be a reason to run a bus every ten minutes. There’s never going to be an incentive for Countdown to open a shop one kilometre down the road from New World. The cafes and drycleaners and florists will never set up across the street.
Here are a few examples of the kinds of environments that could be enabled by intensification. Importantly, these aren’t high-density neighbourhoods – they tend to be composed of terraced houses, row houses, and 4-6 storey apartment buildings rather than massive high-rise towers.
Here’s Greenwich Village, Jane Jacob’s old hood and one of Manhattan’s medium-density neighbourhoods. Look at how many retail and dining choices the residents have:
Here’s a typical cafe in Paris, another city that’s great due to its density and mix of uses. The city’s awash in local cafe and restaurant options because it is dense enough to support lots of them.
Here’s an example from San Francisco – the Castro district, which is one of the spiritual homes of gay and lesbian culture in North America. Medium densities in the area support fantastic (if a bit off-the-wall) nightlife.
And finally, one from Auckland: this is the Elliot Street shared space, which never would have happened without the apartment boom in the city centre. I bet a lot of people around Auckland are looking at how great this is and asking, “when will my neighbourhood get something like this?” The answer is: When your neighbourhood has enough people to support it!
So, what would you like to see happening in your area? Do you think that having a few more people around would help it happen?
Demographia is a pro-sprawl think tank in the USA that publishes density and house price data for cities across the world. They’re often seen using their statistics to argue that the only way to deliver affordable housing is with suburban fringe expansion into greenfields land.
Demographia’s data on housing affordability has come under fire in the past for slipperiness with definitions and misleading choice of measures. But their analysis of population density has gotten less attention – although it’s even more riddled with errors.
Demographia’s approach to calculating density is simple but misleading. They have simply calculated the total number of people in each city and divided it by the total land area covered by that city – including unpopulated areas like parks and reserves. This measure of average density is actually quite irrelevant. For example, Demographia uses it to claim that Los Angeles is more dense than New York.
As Peter outlined in this recent post, what is much more relevant is the density of the neighbourhood that the average person lives in, rather than the density of the average acre of land in the city.
For argument’s sake, consider a village of one hundred acres with one hundred residents. By the measure of area weighted density the density is simple, one person per acre. Does this represent the reality of how people live? Well it could, if everyone lived alone in a separate house on an acre of land. But what if they didn’t? What if everyone lived in a single apartment block in the middle of town that sat on one acre of land? Well then the density the people actually live at would be 100 people per acre. That’s a hundred times more dense… but the same density by Demographia’s measure!
And what if it were something more complex? What if a quarter of the town lived in the one apartment building, half lived in eighth-acre sections around it, and the remaining quarter were spread out over the rest of the land? Doesn’t that sound a bit closer to the reality of most cities? One person per acre means nothing for this theoretical town, half the people live at eight times that density and a quarter at fifty times the density.
Just in case you’re still unsure, in the image below the dots represent dwellings and each box has the same number of dots in it. Overall they have the same average density however in reality they would feel like two very different places.
In short population-weighted density is a much better indicator of the density of the neighbourhoods people chose to live in, and a much better way to describe cities and housing.
With that in mind, it was a simple task to take Peter’s data and throw it on a chart. In simple terms these show how many people live in neighbourhoods (Census meshblocks to be precise) grouped by density in Auckland, Wellington and Christchurch. I’ve also picked out the density level that Demographia says each city is.
It’s easy to see a few things here. First of all we can see that neighbourhood density can vary quite a lot within cities. One number just can’t describe how people live. Second, we can see there is something of a bell curve. Most people live within the middle range of densities, those living very low or very high are small in number, but that middle is actually quite broad. Third, we can see how far off Demographia is. Their supposed summary statistic isn’t anywhere near the middle of the curve, it’s actually near the bottom in each case.
For example it seems the Demographia figure describes the density at which roughly five percent of Aucklanders live. Nine percent live at lower densities, and 86% live at higher densities. Many people live in neighbourhoods that are two or three times more dense than Demographia’s misleading average. In short, Demographia’s figures are irrelevant for the vast majority of Aucklanders (and Wellingtonians, and Christchurchers). They don’t reflect how the majority of people choose to live.
Sorry Demographia, your data is plain useless.