The Connected City
The Connected City
How Networks are Shaping the Modern Metropolis
Zachary P. Neal
Michigan State University
Contents
List of Method Notes
List of Figures
1 INTRODUCTION: Why cities? Why networks?
Micro-urban Networks: Networks within Cities
2 COMMUNITY: Lost or found
3 SUBCULTURE: Finding your crowd in a crowd
4 POLITICS: We don’t want nobody nobody sent
Meso-urban Networks: Cities as Networks
5 FORM: Getting from here to there
6 FUNCTION: Working together
Macro-urban Networks: Networks of Cities
7 REGIONAL: From city to metropolis
8 NATIONAL: The real action is between cities
9 GLOBAL: Nylon holds the world together
10 CONCLUSION: The new science of urban networks
Notes
References and suggested reading
Index
Method Notes
1. The Matrix and Sociogram
2. Complete Networks and Ego Networks
3. Size and Density
4. Collecting Social Network Data Using Name Generators
5. Homophily
6. Transitivity and Closure
7. Two-Mode Networks
8. The Ethics of Social Network Research
9. Cliques
10. Power in Exchange Networks
11. Diffusion through Cohesion and Structural Equivalence
12. Walks, Paths, Distance, and Reachability
13. Centrality
14. Connectivity
15. Roles and Block Modeling
16. Centralization
17. Missing Data
18. Location Quotients
19. Functional Polycentricity
20. Gravity Model
21. Single Linkage Analysis
22. Valued and Directed Networks
23. Planar Networks
24. Edge Betweenness
25. Visualization
26. Mantel Test and Quadratic Assignment Procedure
27. Small World Networks
28. Scale Free Networks
29. Communities
Figures
Figure 1.1 Nested Levels of Urban Networks
Figure 2.1 A ‘Liberated’ Community
Figure 2.2 Network Conceptions of Community
Figure 2.3 Network Structure and Social Capital
Figure 3.1 Social Circles
Figure 3.2 Two Views of Subculture
Figure 3.3 Transitivity and Group Formation
Figure 3.4 Degrees of Network Closure
Figure 3.5 The Duality of People and Groups
Figure 3.6 Networks and Voluntary Associations in Blau Space
Figure 4.1 A Reputational Influence Network
Figure 4.2 A Decisional Influence Network
Figure 4.3 Types of Exchange Networks
Figure 4.4 Brokerage in Exchange Networks
Figure 4.5 Dependence in Exchange Networks
Figure 5.1 The Bridges of Königsburg
Figure 5.2 Types of Street Network
Figure 5.3 Two Approaches to Mapping Street Networks
Figure 5.4 Street Connectivity in Urban and Suburban Neighborhoods
Figure 5.5 Tertiary Streets and T-Communities
Figure 5.6 Street Networks and Urban Land Use
Figure 6.1 Forms of Interorganizational Interaction
Figure 6.2 Structures of Network Governance
Figure 6.3 Service Delivery Networks
Figure 7.1 Geographically Nested Macro-urban Networks
Figure 7.2 Functional Conceptions of Metropolis
Figure 7.3 Centrality in Urban Regions
Figure 7.4 Three Conceptions of Polycentricity
Figure 7.5 Commuting Networks
Figure 8.1 Trade between major ports in 1820 and 1840
Figure 8.2 Development of a National Urban Trade Network
Figure 8.3 Development of a National Urban Finance Network
Figure 8.4 Development of a National Urban Transportation Network
Figure 8.5 Planes, Trains, and Automobiles
Figure 8.6 Types of Airline Route Networks
Figure 9.1 Early Global Urban Networks
Figure 9.2 Two perspectives on cities in global networks
Figure 9.3 A Typology of Global Urban Linkages
Figure 9.4 Economic Approaches to Measuring Global Urban Networks
Figure 9.5 Centrality and Power in Global Urban Networks
Figure 10.1 Random and Scale Free Networks
1
INTRODUCTION
Why cities? Why networks?
This is, first and foremost, a book about cities. But, why write about cities?
Because at least since the industrial revolution, people have been moving to cities in
search of both opportunity and stimulation. The shift of the world’s population
into cities – urbanization – is clear from a few simple statistics. In 1800, only 3% of
the world’s population lived in cities, but by 1900 this number had increased to
14%, and passed 50% in 2008. This number is expected to continue climbing, to
70% by 2050. The rapid urbanization of the population has been even more
dramatic and complete within the United States, where 6% lived in cities in 1800,
nearly 40% in 1900, and now over 80%. Clearly, then, cities are worth studying
because they are where the majority of people are today.
But, cities are not just dense clusters of people. They are also dense
clusters of all sorts of human activity including research, commerce, tourism, and
culture. Indeed, even in the past, when the majority of people lived in the rural
countryside, cities were still vibrant centers of activity. Major cities of the classical
age like Athens and Rome cities served as centers for religion and government,
where pilgrims and concerned citizens traveled to worship and be heard. During
the medieval period, cities and towns served as bustling marketplaces where local
farmers and worldly merchants came together to offer their products for sale.
Later, large institutions like universities but also small ones like coffee houses
sprung up in cities during the age of enlightenment, which helped bring together
like-minded individuals seeking to break with rural superstition in the pursuit of
science. Even today, those living in small towns frequently visit cities to take part
in their recreational amenities like museums and parks, and to patronize their
diverse commercial establishments like unique shops and ethnic restaurants. So,
cities are not just where the people are today; cities are where the majority of
human activity has always been.
In addition to being a book about cities, this is also a book about
networks. But, again, why write about networks, especially in a book about cities?
The goal of this book is to demonstrate the answer to this question. Scholars have
long recognized that cities play an important role in society, and have been trying to
understand how cities work for centuries. Using networks to understand cities can
be helpful in several ways1. First, networks can bring greater precision to existing
theoretical concepts. For example, Robert Park’s classic description of the city as
“a mosaic of little worlds which touch but do not interpenetrate” becomes more
concrete when we think about how an urbanite’s social network may include ‘work
friends’ and ‘school friends’ who don’t know one another2. More recently, a
complex topic like globalization is more manageable if we think about it as simply
the effect of distant places like London and New York being connected to one
another by networks of airline traffic or internet communication. Second,
Why cities? Why networks?
2
networks offer a different way of thinking about how the world is organized, and
thus can help us consider new (and potentially better) answers to some old
questions. For example, it is hard to understand what holds a neighborhood
together if it is simply a group of people living in a particular area. But, thinking
about a neighborhood as a set of people that regularly interact with one another
sheds light on how neighborhood associations and block parties are possible.
Finally, networks offer a way to bridge a major conceptual gap in the social sciences
known as the micro-macro problem: how do little individual behaviors give rise to big
urban phenomena. For example, while it is not immediately obvious how broad
patterns of segregation throughout a city can arise from the behaviors of individual
people, the linkage is easy to see when we consider the fact that each individual
tends to form friendships with people who are similar to themselves. In examining
a range of urban issues like these from a network perspective, this book aims to
explore and demonstrate how networks can be useful for making sense of cities.
What are networks?
The idea of networks has been around quite some time, and has been used in many
different ways. In this book, networks are viewed as specific and observable patterns of
relationships that can be directly or indirectly examined. Of course, these relationships
might take many different forms, and they might connect people, or buildings, or
cities. The key point is that, whatever the relationships are and whatever they
connect, networks have a specific and observable content that can be studied.
Focusing on this type of network represents a distinctive way of trying to
understand the social world that directly focuses on these patterns or structures.
Therefore, it is important to consider what it means to adopt a network-based
approach to thinking about cities and urban life, and how it differs from other
more traditional approaches.
Most social science research focuses on the attributes of the things being
studied. In some cases these are objective characteristics like a person’s age or a
city’s population size. In other cases they are more subjective characteristics like a
person’s attitudes toward other racial groups or a city’s political climate. These
individual characteristics are then used, perhaps with a methodology like multiple
regression or ANOVA, to explain some phenomenon. For example, a study on
neighborhood diversity and openness might examine the ages and racial attitudes of
a large sample of people in an attempt to understand why some communities are
more welcoming of difference than others. Similarly, a study of urban
unemployment might examine the sizes and political climates of US cities to
understand why some areas have fewer available jobs than other areas.
This traditional approach to studying the social world has become the
standard for a number of reasons. The vast majority of existing data, like that
available from the US Census Bureau, provides information about the
characteristics of individual people, neighborhoods, or metropolitan areas. And,
when existing data sources are insufficient, collecting additional data on the
characteristics of individual people or places is relatively straightforward using
Why cities? Why networks?
3
surveys. Additionally, the methods used to analyze such individual-level data are
commonly taught in introductory statistics courses, and are simplified using widely
available software. But, this traditional approach suffers from two major
shortcomings. First, it is categorical: it places things into pre-defined categories – a
person’s age or attitude, a city’s size or political climate – and uses those categories
to explain the world, even though we know the world is not so neatly organized
into boxes. Second, it is individualistic: it treats each person or place as
independent and isolated, even though we know that people and places are
connected to one another through relationships like friendship or political alliance.
Focusing on the networks or relationships that exist among people or
places, rather than their individual characteristics, overcomes these challenges.
Such a network-based approach, sometimes called structuralism because is examines
the structure or pattern of relationships, does not depend on pre-defined categories
and does not treat social creatures as independent. First, it is non-categorical:
instead of grouping people and places into categories based on characteristics like
age or population size, adopting a network approach instead considers which
people and which places interact with each other. Second, it is not individualistic
but relational: instead of treating them as independent, a network approach
recognizes that people and places influence one another through their relationships.
To summarize, while traditional social science approaches concentrate on the
individual characteristics of people or places to explain and understand the social
world, a network-based approach concentrates instead on the complex patterns of
relationships between these people or places.3
Although researchers have been thinking about and using networks for a
long time – even longer than many of the more widely used approaches – they
represent a significant departure from traditional social science.4 As a result, there
are many misconceptions about networks and structuralism. Some believe
networks are simply a quantitative methodology for data analysis. While it is
certainly true that ‘social network analysis’ is often a numbers-based method for
examining data, many researchers examine networks in more qualitative ways
through interviews and other methods, focusing on issues like how people think
about and manage their social networks. Similarly, networks and structuralism
more generally are not simply a methodology for analyzing data, but also a way of
thinking about the social world; they are equal parts methodological approach and
theoretical perspective. Another widely held misconception about networks is that
they are complicated and abstract. Again, while some network analyses may be
very complex, the basic ideas are really quite simple: relationships are important,
and different patterns of relationships have different consequences in the social
world. This book aims to demystify networks and network analysis, and to
demonstrate that understanding them need not be rocket science. A final common
misconception is that a network-based approach ignores other important
contextual factors like culture. Quite to the contrary, the networks – the patterns
of relationships among people, institutions, and whole cities – are the context! By
looking carefully at how people or cities are related to one another, we can often
gain a better understanding of where “culture” comes from.
Why cities? Why networks?
4
Not a book about “networks”
While the previous section clarifies what networks are, it is also helpful to be clear
what networks are not, at least as they are considered in this book. This book
avoids viewing networks as a loosely defined, commonsense, or metaphorical
notion that society is built up through connections between people who are related
to one another as if linked in a network. The conception of networks as simply the
idea that people are connected to one another, and that such connections are
important, has been advanced by many scholars writing at different times and in
different traditions. For example, German social philosopher Karl Marx (1818 –
1883) argued that “society is not merely an aggregate of individuals; it is the sum of
the relations in which these individuals stand to one another.”5 Similarly, American
sociologist Charles Cooley (1864 – 1929) suggested that “a man may be regarded as
the point of intersection of an indefinite number of lines representing social
groups.”6 Finally, English anthropologist A. R. Radcliffe-Brown (1881 – 1955)
noted that “human beings are connected by a complex network of social
relations.”7 While there is no question that such claims are true and are closely
related to the topic of this book, they are also relatively obvious and are the basis of
nearly all of the social sciences and humanities. As a result, they tell us very little
about what networks are or how they work, frequently because they do not identify
exactly who or what is connected, or how. To understand networks, it is important
to observe, measure, and analyze them. This also requires recognizing that
networks are not merely useful metaphors for how the social world is structured,
but really are the way the social world is structured. Thus, this book adopts the
stance that people and cities are not merely related to one another as if connected
by a network, but are in fact connected to one another by real, measurable
networks.
In addition to being used as a metaphor, the word ‘network’ is sometimes
used to refer to things other than patterns of relationships. Often, a group or
coalition calls itself a network, referring to the fact that its members are somehow
connected to one another. For example, many organizations aimed at combating
social problems, like those associated with globalization, have used the word
‘network’ in their name: Continental Direct Action Network, Third World
Network, The Network of East-West Women. Similarly, groups of cities and city
leaders that come together to solve common problems also frequently describe
themselves as networks, including the Healthy City Network organized by the
World Health Organization, the Creative Cities Network organized by UNESCO,
and the Eurocities Network of major European cities. Although these people,
organizations, and cities might be connected to one another by the patterns of
relationships among them, simply calling something a network does not make it
one.8
In other cases, the word ‘network’ is used as a verb to describe the act of
‘networking,’ or the deliberate formation of relationships to achieve a desired end.
Often notions of networking appear in business settings, where individuals might
Why cities? Why networks?
5
attend networking events like receptions and charity dinners to establish new
business contacts and solicit potential clients. In other cases, politicians might be
described as networking when they make public appearances and take an
opportunity to shake constituents’ hands. And, the act of networking has now
expanded beyond the corporate and governmental arenas; nearly everyone engages
in some form of networking, facilitated by social networking sites like Facebook or
Twitter. Such technology is used by people to form new relationships, to maintain
existing relationships, and to rekindle past relationships, all in an effort to stay
connected or to grow one’s social network. While networking, whether in person
or online, is certainly important today, it is only a tiny sliver of the formal study of
networks as a social phenomenon. In this book, the focus is not so much on
organizations that call themselves networks or on networking to make friends and
find clients, but on how these institutions and behaviors influence cities and life in
them.
Finally, this book does not directly address the theoretical perspective
known as Actor-Network Theory (ANT). Although it includes the word ‘network’
in its name, it shares little in common with the network and structuralist
perspectives that are the topic of this book. ANT emerged in the French poststructuralist tradition, and initially focused on analysis of technological systems,
where relationships among social actors like people are considered, but also the
relationships among the ideas they create and the things they use.9 The theory aims
to explain how these people, concepts, and objects come to be related to one
another, and how these relationships influence social interactions. Often the focus
is on how things like laws and other social conventions develop and acquire
meaning through their relationships to people and other ideas. More recently, the
ANT approach has been applied to the study of cities.10 Although this has become
an influential approach to understanding how cities develop, it is not directly
considered here, except briefly at the end of chapter 4, where the networks of
urban politics are contrasted with the politics of urban networks.
To summarize, although the idea of networks has been used in a variety of
ways, and has even found its place in everyday talk, the focus of this book is
relatively specific and not overly complicated: how do networks, as observable
patterns of relationships, influence cities and help us understand life within them?
Theory or methodology?
One unique feature of networks – indeed, one that is a common source of
confusion – is its simultaneous role as both a theory and a methodology. In the
social sciences an idea is often thought of as either theoretical like ‘social class’ or
methodological like ‘multiple regression.’ However, networks offer both a
theoretical framework for understanding the world and a methodology for using
this framework to collect data, test hypotheses, and draw conclusions.
A number of excellent books have been written about networks as a
methodology.11 While they serve as useful reference guides, the trouble with
methodologically-focused books is that they are often boring to read and offer only
Why cities? Why networks?
6
limited applications that illustrate how the techniques can be used to answer
interesting questions. Similarly, a number of equally good books have been written
that use network theories to examine cities and urban life.12 These often tell
interesting and engaging stories about cities, and use the idea of networks to
understand old issues in new ways, but they rarely explain the nuts-and-bolts of
network methods.
This book aims to combine discussions of networks as both theory and
methodology.13 The bulk of the text uses network theories to consider questions
about how cities work and how urban life is organized. When a new
methodological concept or technique is introduced, a separate ‘method note’ is
included that provides a brief introduction to the practical issues of using networks
in research. Just as with any complex methodology, each of these method notes
builds on the others that precede it. However, they do not assume any prior
experience with network analysis methodologies, or any particularly sophisticated
mathematical background beyond addition and subtraction. Although networks are
often perceived as mathematically complicated, this is a misconception. Anyone
able to do basic math, and draw circles and lines, already has the ability to use
network methods.
A number of software packages designed for examining networks are
available. Two commonly used programs, UCINET and NETDRAW, are available
to download at http://www.analytictech.com/ucinet. The former is used to
conduct network analysis, while the latter is used to draw sociograms or graphical
depictions of networks. The UCINET commands that correspond to the
methodological concepts introduced in the text are indicated in the method notes.
These programs include several example network datasets that can be used for
experimenting with different analyses. Additional example network data is available
from
the
UC-Irvine
Network
Data
Repository
at
http://networkdata.ics.uci.edu. Such programs are useful for examining
networks, but because they cannot tell the user which type of analysis to perform or
how to interpret the results, they are not a substitute for understanding network
analysis. That is, although they can produce results and draw sociograms with
some random pointing and clicking, it is important to understand where these
results come from and what they mean. The method notes throughout this book
are designed to introduce some common network analysis techniques so that the
software can be used as a tool rather than a magic wand.
With this layout of main text and method notes, it is possible to read this
book in a number of ways. For the most complete introduction to the theory and
method of networks in the urban context, reading both the main text and the
occasional method notes from beginning to end is best. However, for the reader
who is primarily interested in the relevance of networks for cities, but not on the
methodological details, the main text is designed to be comprehensible and to flow
smoothly even if the method notes are skipped. Similarly, for the reader who is
primarily interested in learning how to use networks in research, the method notes
can be read in order as a brief introduction to network methods.
Why cities? Why networks?
7
Organization
In the 1960s, geographer Brian Berry argued that cities could be examined at
multiple, nested levels of analysis, by viewing cities as systems within systems of
cities.14 This book adopts the same general idea, but extends it by recognizing first
that cities and urban life can be examined as networks, and second that these urban
networks can be examined at many different levels that build upon one another.15
Thus, it focuses on the three types or levels of urban network depicted in figure 1.1:
micro-, meso-, and macro-urban networks. Each level requires a distinctive set of
theoretical and methodological tools that make it possible to consider different
types of questions. At one extreme, some researchers examine mainly the networks
that exist within cities, like the social relationships among neighbors that generate a
sense of community and belonging. At the opposite extreme, others focus
primarily on networks between cities, like the web of nonstop airline flights that
make face-to-face business meetings possible. What makes this book unique is that
it aims to collect and synthesize the insights and tools of the multiple scales of
urban networks. The chapters are grouped into three major sections by the level of
analysis and scale of network they focus on: micro-, meso-, and macro-urban
networks.
Figure 1.1 Nested Levels of Urban Networks
Micro-urban Networks. The smallest scale urban networks that might be
examined are the personal social networks that link together the individuals living,
working, and playing in cities. Legendary urbanist Jane Jacobs poignantly described
such relationships, noting that “Most of it is ostensibly utterly trivial but the sum is
not trivial at all. The sum of such casual, public contact at a local level…is a feeling
Why cities? Why networks?
8
for the public identity of people, a web of public respect and trust, and a resource
in time of personal or neighborhood need.”16 While some of the personal social
networks of urban dwellers are informal and casual, like the sidewalk friendships
Jacobs describes, others are more formalized, like the relationships between a local
politician and his or her constituents. But, whatever form they might take, the
linkages among a city’s people play an important role in city life. The chapters in
the first part of the book explore how.
Chapter two asks what role community plays in modern city life? Some
have argued that when people move to big cities, community and feelings of
solidarity are lost and get replaced by isolation and feelings of loneliness. But,
adopting a network-based approach, others have argued that community is alive
and well in the numerous and varied relationships that city dwellers maintain.
Chapter three then considers how, in such busy and crowded places as modern
cities, social groups like subcultures and ethnic enclaves form. The formation of
such tight-knit groups might seem impossible in the big city, but from a network
point of view, having a close circle of friends and acquaintances who all know one
another and belong to the same clubs and organizations helps create pockets of
order in a sea of chaotic diversity. Finally, chapter four examines why some people
are influential in running cities and controlling urban affairs, while others are
relatively powerless. While political and social influence might seem to depend on
individual characteristics like one’s leadership ability or wealth, a person’s position
in an urban social network can be even more significant.
Meso-urban Networks. Transitioning to a larger scale of network, rather
than focusing on the networks within cities, the second part views the city itself as a
kind of network. More specifically, the second part of the book conceptualizes the
city as a collection of intersecting, interacting, and overlapping networks that bind
the many different parts of the city into an organic whole like a living organism,
giving it both form and function. Unlike the personal social networks within cities,
the contents of these networks are not people, but spaces and institutions. Chapter
five concentrates on cities’ physical layout – their form – to consider how different
physical arrangements influence how we experience the city. More than just
aesthetics and efficiency, a city’s infrastructure networks – its streets, sidewalks,
mass transit – guide us to use the city in specific ways. Then, chapter six focuses
on how all the services, organizations, and agencies get coordinated to keep a
complex city functioning, rather than dissolving into confusion. The delivery of the
wide range of urban services like trash collection, health care, education, and
recreation are rarely the result of a single centralized plan. More often they are
made possible by a complex network of inter-organizational relationships that allow
providers to join forces through collaboration, or to dominate through
competition.
Macro-urban networks. The third part of the book shifts to a still broader
level of analysis and larger scale of network, to focus on networks that link entire
cities to one another. Scholars focusing on these networks of cities have argued
that they can be considered within three geographic domains: regional, national,
and global.17 The chapters in this section are organized along these lines. First,
Why cities? Why networks?
9
chapter seven asks how a city becomes a metropolis by looking at how groups of
cities in a particular region are linked together by networks of commuting workers,
partnerships among business firms, and cooperation between local governments.
These regional city networks can transform a single city with a single downtown
area where all the activity is concentrated into a metropolitan area where activity is
concentrated in multiple places. Then, chapter eight considers how cities are
related to one another across longer distances and larger areas like an entire
country. Often inter-city networks, when they occur on a national level, serve to
establish a national urban system in which cities play specialized economic and
social roles that require a level of urban interdependence. Finally, chapter nine
turns to the global arena, asking what makes a handful of major ‘world cities’ like
New York, London, and Tokyo so important. Is their importance related to their
giant population size, their prominent businesses, and their role in history, or is it
due to their position in a world city network?
The concluding chapter explores some of the universal features that cut
across networks at these different levels. For example, in a phenomenon frequently
described as ‘six degrees of separation,’ it is common for people who do not know
one another to have the same friends, or friends of friends. This often leads
people, when they discover that they share mutual acquaintances, to remark: “Gee,
it sure is a small world.” But the ways that streets connect to one another, and that
cities around the world maintain diplomatic ties with one another, tend to follow
the same pattern. The big city is a small world indeed, but just how small?
Similarly, although most of us have only a handful of friends in our social network,
we usually know someone who seems to know everyone. But the same is true for
city politicians and urban organizations; most have just a few connections to others,
while a few have the lion’s share. Why, and what are the risks and benefits of such
inequality? These patterns can be seen not only at all levels of urban networks, but
indeed in virtually every type of network ranging from the circulatory system of an
animal to the world wide web.
Throughout each of these chapters, the focus is more on broad patterns
than on facts and figures. That is, the purpose of this book is not to provide a
detailed discussion of specific research findings. Because the field of urban
networks is still rapidly developing, to do so would make it outdated as soon as it is
published. Instead, this book aims to explore how a network perspective can be
useful for making sense of cities and urban phenomena.
Acknowledgements. Not surprisingly given its topic, this book would not
have been possible without a large network of people, institutions, and cities that
provided invaluable support and inspiration. I first want to thank Steve Rutter and
Anthony Orum for recognizing the importance of urban networks and the value of
a book like this one. But, I myself did not always realize the importance of, much
less understand, network methodology or urban networks. For that, I owe thanks
to Yoosik Youm, Pamela Popielarz, and Dennis Judd. In a book about cities,
places matter too. Nearly a decade living in Chicago helped me appreciate the
many levels of urban life, from the well-defined neighborhoods with their unique
Why cities? Why networks?
10
characters, to the elegance of Burnham’s only partly realized plan, to the global
reach of the city’s cultural events. In contrast, the long winters in East Lansing
proved a powerful motivator to stay indoors and focus on writing. At Michigan
State University, my students in SOC931 (Spring 2011 & 2012) and SOC361 (Fall
2011) endured early versions of this book, and their reactions helped me think
carefully about the messages I was trying to convey. In addition, MSU’s
Humanities and Arts Research Program (HARP) and Center for the Advanced
Study of International Development (CASID) provided critical funding for this
work. Finally, I must thank my loving wife Jenna, without whose reassurance I
would
never
have
bothered
to
finish
even
chapter
one.