We now analyze the quantitative characteristics of networks of connectivity at the national and urban levels. We begin by describing nationwide connectivity patterns, then those of the nation’s largest city, Abidjan. We then discuss how certain quantitative signatures of mobile telecommunications connectivity can characterize how well integrated an urban system is and measure the presence of urban agglomeration effects.
Telecommunication patterns in Côte d’Ivoire’s urban system
For a nation to develop, it is essential that each of its locations is integrated into an urban system made up of inter-dependent cities that exchange people, goods and information (Fujita and Mori ). This is because it is across cities of different sizes that the advantages of large urban areas, in terms of innovation and organization, pay off. In this view, development happens through the incorporation of new ideas and organizational forms into the structure of industrial and primary production, which, in turn, form the principal basis for the economies of smaller cities, and the material basis for nations as a whole (Christaller ; Lösch , Fujita et al. ).
In theories of central place (Christaller ; Lösch ) later elaborated by modern economic geography (Fujita et al. ), the crucial feature that provides the basis for intercity dependences is a functional hierarchy of economic functions. This means that the largest city in the system contain (but is not self-sufficient in) all economic functions observed in smaller ones, but not the reverse. As such, larger cities supply services (innovation, information, organization) to smaller cities in their territory, primarily in exchange for food and other material goods. The largest city in an urban system is thought to service, in this way, an entire nation. Despite some urban specialization, such as in large-scale manufacturing, these trends are characteristic of most developed nations (Mori et al. ; Hsu ). Here we investigate if these patterns are characteristic of the Ivorian system of cities.
Detailed and reliable information about economic functions is still hard to obtain at the city level, especially in developing nations. Nevertheless, telecommunication data gives us an entry point to investigate to what extent Côte d’Ivoire’s urban system is spatially integrated, and to measure the roles of distinct cities in light of the expectation of a national urban hierarchy expressed in terms of telecommunication call flows. In other words, it is not enough to assume that cities of different sizes serve purposes in a larger network without knowing how they are connected as a network. With telecommunications network data, this becomes possible.
In this section, we examine the structure of the networks of telephone calls between prefectures in Côte d’Ivoire. A map of the total number of calls (placed and received) between any two places in the urban system shows, as would be expected from central place theory arguments, the importance of the largest city, Abidjan (about 3.8 million people) (Figure 2). The connection to Abidjan is expressed in terms of the diversity and strength of calls exchanged with many other cities in the nation. However, even at this level we start to observe that links to Northern and Western parts of the country are relatively sparse. The political capital Yamoussoukro also plays no particularly strong role in this network, despite its expected behavior of connecting to the two large population centers, Abidjan and Bouaké (pop. ~775,000 in 2002).
These patterns become clearer when we consider calling behavior between any two places on a per capita basis: That is, when we ask what the typical calling patterns of an individual subscriber in a given city may be. Calls placed (Figure 3A) and received (Figure 3B) per capita show that larger cities, Abidjan in particular, are large hubs in the national communications network. These calling patterns show that much of the nation of Côte d’Ivoire is actively listening to what happens in Abidjan. As for Abidjan itself, most of the calls it places (84%) are to other parts of the city. (Note that it does not follow necessarily that Abidjan obtains its information from other parts of the city, as the large developing metropolis likely also possesses strong links to other international cities, not provided in the D4D dataset).
Apart from Abidjan, the second largest city, Bouaké, plays an analogous role, but more limited to its immediate neighboring region. Interestingly, the political capital Yamoussoukro, does not escape this pattern: its strong connections to the two largest cities are more in placing calls rather than receiving them. Other economically important regional centers, such as San Pedro (the second largest port, after Abidjan), have more mixed patterns of connectivity, separate from those of the other larger cities. Though already seen in Figure 2, the northern and western parts of Côte d’Ivoire are also largely disconnected from the main economic and political centers of Côte d’Ivoire when viewed on a per capita basis.
To quantify these patterns of communication fit a simple gravity model to call data. This models the volume of calls between two places i and j, C
where G is a constant, N
are the populations of the two cities, and d
is the (Euclidean) distance between them. The parameters g and G are obtained by fitting Eq. (1) to call data. We obtain a reasonably good fit (R2 = 0.42) with g = 2.13 (95% confidence interval [2.02,2.24]) and G = 0.002 (95% confidence interval [0.001,0.003]). In practice, the exponent g is empirically observed to vary for different datasets, for different nations at different times, around the value g = 2. The present value is similar to that obtained by (Krings et al. ) for Belgium.
We now use this best-fit gravity model as the generator of a set of null expectations for the volume of calls between any two places in a well-developed urban system. Figure 4 shows the residuals of the gravity model fit, as the difference between the logarithm of actual calls and the gravity model prediction: For x
> 0 (red) two places communicate more than expected by the gravity model, while for x
< 0 (blue) the converse is true. We observe a pattern where the south of the country, and especially its southwestern region, including San Pedro, is the most interconnected. Though the population is sparse in the region this finding may illustrate the burgeoning power of the coastal port industry and its relation to inland cocoa and coffee production. Conversely there is a much weaker pattern of connectivity from the South to the North and from East to West (illustrated also in Figure 2, Figure 3). These structured patterns of under-connection are somewhat surprising as Côte d’Ivoire is often thought to be primarily divided between a poorer, more Muslim, north and a more affluent, Christian South.
This network structure suggests that the Ivorian urban system is still very much incipient. Most cities display strong communication links regionally, but it is clear that even Abidjan (the economic capital) and especially Yamoussoukro (the political capital), though displaying a greater reach than smaller cities, fail to maintain a network of communication with most of the nation, especially the North and West, which are, not coincidentally, the poorest parts of the nation.
When regions are disconnected, it is more difficult for the nation to take advantage of the social, human and economic capital produced in various parts of the country. This predicament of inaccessibility becomes even direr when communications and travel infrastructure are not fast, affordable and reliable, and can be deleterious to the nation’s economic progress. This suggests that a path for national development must entail improvements in the integration of the nation as a whole (Hardy ; Goddard and Gillespie ; The World Bank ), and should be facilitated and accompanied with the observation of increasing call rates between all places, and especially between the larger cities and the western, southwestern and northern parts of the country. We discuss the effects that may serve as indicators below.
Urban agglomeration effects
Large cities are often described as the social, political and economic engines of most (developed) nations. However, it has also been argued that recent urbanization in many parts of Africa has apparently failed to deliver on its promise for economic development (The Economist Online ) and has proceeded without much to show in the way of measurable economic growth. These issues are subtle, however, as we discuss below in the context of Côte d’Ivoire.
Generally, historical and contemporary patterns of national development very much depend on the socioeconomic dynamics that happen inside a nation’s largest cities and in particular on the ability of these places not only to grow but to realize increases in social interactivity that can lead to larger and more sophisticated economic specialization and interdependence; organizational and technological innovation; and the seizing of latent economies of scale in services and infrastructure (Bettencourt et al. ; Jones and Romer ).
Arguments from complex systems theory and from urban economics emphasize the role of agglomeration economies in all these processes: the output of socioeconomic processes rises on a per capita basis with the size of cities. This is interpreted in terms of the possibilities for interaction created by spatial and temporal concentration of people in cities (Bettencourt , Lobo et al. ). However, even if these conditions are met, the question remains whether cities realize these interactions for good or for ill. Negative consequences of increased human interactivity can also occur, in terms of increases in crime rates, the prevalence of infectious diseases and the proliferation of small-scale informal economic agents. The cities of Côte d’Ivoire, and Abidjan in particular, manifest these various consequences of urbanization: The good and the bad are very much intertwined, as we discuss below. Telecommunications data can help in the determination of not only which cities are involved in this type of growth, but also provide metrics of to what extent agglomeration effects are realized in each place.
In addition to analyzing nationwide regional connectivity (Figures 2 and 3), and the deviation from an expectation of these patterns (Figure 4), we also examine the communication patterns in the region and central city of Abidjan (Figures 5 and 6, respectively). At the metropolitan level it is clear that Abidjan thoroughly integrates its central communes, between and within surrounding population centers, such as Anyama, Bingerville, Bonova, Dabou, Grand–Bassam and Songon (Figure 5).
Central communes in the city exchange information even more frequently than with these other adjacent areas (Figure 6). Especially noteworthy are the almost parallel roles of the two population centers of Yopougon (most populated commune) and Cocody (most affluent residential district), and in a different way the commercial and business centers of Adjamé and Plateau. Interestingly, the commune of Abobo, which also has a large population, to a large extent of internally displaced migrants, is less connected than Yopougon to the rest of the city. Nevertheless, these figures strongly suggest strong communication patterns between ethnically, functionally and economically different parts of the city, which are a sign of functioning urban center as a mixing social network (Bettencourt ).
This suggests that even if Côte d’Ivoire remains relatively disconnected as an urban system, local socioeconomic connectivity within cities seems to thrive (most clearly in Abidjan) and can facilitate general processes of urban agglomeration.
To test this idea in greater detail beyond Abidjan, we perform a simple scaling analysis for the total number of calls received by each prefecture as a function of their population. These patterns are well described on average by a power law function (Bettencourt et al. ; Bettencourt and West ; Bettencourt ) where the connectivity, C, is a function of population size N, C = C0Nb. The parameter b-1 measures the on average increase in social connectivity per capita with city population size. We observe, b = 1.26 (95% Confidence Interval [1.19, 1.34]) implying that connectivity per capita increases by about 26% with each doubling in population size (Figure 7A and 7B). These scaling effects are in line with patterns recently measured for analogous telecommunications data in Portugal and the United Kingdom (Schläpfer et al. ) and predicted by urban scaling theory (Bettencourt ). They suggest a general acceleration of social economic processes with city size in agreement with many other nations, developing and developed (Bettencourt et al. ; Bettencourt and West ; Bettencourt ). In line with the observations of the previous section, upon isolating internal calls, we find that growth in connectivity with population size that is due to internal calls within each city is even faster, with a b = 1.49 (95% Confidence Interval [1.39, 1.58]). This means in practice that as Ivorian cities grow the fraction of all calls that is internal to the city increases. In Abidjan, 46% of all calls initiated in the city are to callers within the city.
Moreover, the joint signature of urban agglomeration effects and of an urban hierarchy should be visible in patterns of diversity of connection and city size (and therefore of economic productivity, see below), as has been observed for the U.K. using telecommunication networks (Eagle et al. ). We find similar results showing how simple measures of diversity: the total number of unique places called from a city and the Shannon entropy of such call patterns (Shannon ), increase on average with city size (Figure 8).
That cities in Côte d’Ivoire generally realize agglomeration effects is good news for national development. However, it is also important to understand what effects of urbanization are enabled by social interactions, benign or malign (Bettencourt et al. ). The recent history of Côte d’Ivoire, which has many parallels with other examples of urbanized Africa and Latin America, indicates that its most recent rapid urbanization is partially the result of conflict and political crises, and less of planned migration to access social and economic opportunity. Abidjan, for example, has grown explosively in population during the last decade of conflict in the region, due to both internally displaced people and refugees from neighboring nations.
Nevertheless, and despite these challenges, rates of poverty in Abidjan are lower than in all other parts of the country (21% compared with 49% for the nation) (International Monetary Fund ), especially in comparison with rural areas. Urban GDP is largely unknown. However general estimates suggest that Abidjan is responsible for about 40% of national GDP, whereas northern, landlocked Bouaké accounts for about 3% and San Pedro, an important port for cocoa exports, accounts for 4%. Accounting for their respective populations results in an annual per capita GDP of 3,677, 1,337 and 4,857 USD respectively, considerably larger than the national GDP per capita of 1,062 USD. Perhaps clearer are the results of the most recent Survey of Living Standards of Households in 2008 (via International Monetary Fund ). Its findings regarding personal income illustrate more fully the relative economic advantages of urban centers and of Abidjan in particular. The findings of this survey estimate that all urban centers in the nation manifest larger incomes than their surrounding rural areas by factors of 1.3 to 1.9 (national average is that urban incomes are 1.82 larger than rural ones). The annual average per capita income in Abidjan is by far the largest in the nation at about 561 thousand CFAF (roughly $1140 USD) compared with 372 thousand CFAF (roughly $695 USD) for the national average. In 2007, Mercer Human Resources Consulting, who rank cities around the world in terms of their quality of life, placed Abidjan as 35th most expensive city in the world! Thus, economic urban agglomeration effects are at play in Côte d’Ivoire, even if national GDP (and incomes) may have recently decreased in real terms, during the last decade of conflict.
Other more sinister urban agglomeration effects point to some of the challenges of development in Ivorian cities. It has been estimated that 4.7% of the country’s population is infected with HIV/AIDS (International Monetary Fund ). According to the same survey, in Abidjan, the prevalence of the virus is much higher, at 6.1%. Already in 1997, about 40% of hospital beds in Abidjan were occupied by HIV/AIDS patients. Urban insecurity is also high, though few reliable numbers exist. The same IMF report stated that in the first half of 2008, out of a total of 62,424 offences to the penal law registered by the National Police, 75% were registered in the district of Abidjan.
In parallel, economies of scale in urban infrastructure, a general characteristic of cities worldwide, seem to be at best only incipient in Côte d’Ivoire. While it is in the nation’s large cities that access to sanitation, treated water, power, and other general services is at all possible these services work mostly intermittently and in small scales, thus squandering some of the possible system-wide savings made possible by large population concentrations. Nevertheless, the already existing urban agglomeration effects and spatial concentration of population in cities presage that Ivorian cities should immediately benefit from realizing economies of scale their urban infrastructure improves. Complex systems theory of cities gives expectations for the general properties for these infrastructural networks as they develop in tandem with socioeconomic quantities (Bettencourt ).
All these results, and many more relating to the concentration of services such as police forces, businesses types (Sleuwaegen and Goedhuys ) and education, strongly suggest that urban agglomeration effects are already at play in Côte d’Ivoire’s cities. However, many of the negative consequences of increased social connectivity, such as high levels of violence and incidence of infectious diseases, may trump some of its economic gains. This pattern is historically typical. Development happens as large problem-plagued cities build infrastructural, political and civic organizations that allow them to systematically tackle problems of population agglomeration (Hall ). How mobile communications may play a new role in enabling such solutions is discussed below.
Entrepreneurship and informality
Finally, and more speculatively, the somewhat poorly known structure of employment and economic entrepreneurship in Côte d’Ivoire suggests that most economic activity in urban centers is concentrated in small and unspecialized organizations, with some exceptions in terms of electricity and cement production, as well as activity in the international ports of Abidjan and San Pedro.
The IMF has, in fact, recently described the informal economy of Côte d’Ivoire as ‘vibrant’ (2009). It is estimated to have engaged roughly 4,107,595 workers in 2002 vs. 1,698,300 workers in 1995, an increase of 142% over 7 years. Much of the informal sector is rural, but informal employment in Abidjan is estimated to be about 75% (United Nations Development Program ).
Given the increases in social connectivity afforded by urbanization and mobile communication, why haven’t larger and more sophisticated firms emerged in Côte d’Ivoire? In economic theory, firms are thought to emerge as a result of the minimization of transaction costs, which must always be incurred in real markets (Coase ). Examples of such costs are purchasing of parts and services external to the firm, supplier and client contracts and personnel hiring. These market costs become prohibitive when sophisticated production, involving the integration of specialized skills, is at play. As a result, specialization and learning occurs frequently inside firms.
Mobile telecommunications play a potentially interesting role in promoting social coordination, minimizing market transaction costs, and in promoting social organization that could result in the growth and sophistication of economic production. Thus, we hypothesize that in many informal economies cell phones may have encouraged on-demand labor arrangements that may, in fact, defeat the potential for larger firms with more extensive division of labor and specialization of knowledge to emerge. Certainly, that seems to be the case of Côte d’Ivoire in recent years (Ilahiane and Sherry ), where, judging from older data from around 1990, the size distribution of firms was characterized by a “missing middle”: most economic enterprises were either large, or very small (Sleuwaegen and Goedhuys ).
The following example from the transportation sector illustrates how informal market solutions have been trumping potentially more efficient large-scale services: in Abidjan, mass transportation is mainly operated by the public company SOTRA. In 2000, after a decade of disinvestment, its services translated into one bus for more than 4,500 inhabitants, rendering inevitable disaffection for its services. To fill this gap for an essential urban service, informal transport operators (using minibuses called “gbakas” and “504 s”) rose to the occasion. Their fleets are estimated at about 6,026 vehicles, while that of regular taxis also swelled to about 8,000 vehicles, with yet another solution (communal taxis or “wôro-wôrôs”) accounting for another 11,971 units. Not only did these informal businesses fill a gap in transportation services, they also illustrate the immense opportunities for integration and formalization of new economic initiatives within the city.
Mobile communications play a significant, though perhaps obfuscated, role in the scaling up in scope and quality of informal urban businesses into modern economic sectors. In a tumultuous economy, where little is guaranteed day-to-day, mobile phones make possible real-time coordination of logistical changes that rely on weather and event conditions, knowledge of flux in consumer demand, and inventories (such as a van). The ability to transfer valuable information in real time, can allow Ivoirians to make more informed decisions as part of their business practices.
New pricing models and innovative uses of telecommunication services may provide necessary incentives to make these businesses visible, measurable and scalable, while preserving their economic basis and essential services to the public. Such measures may also promote greater trust and satisfaction at the urban level and new economic models that can be exported to other cities.
Promoting social connectivity for development
We have noted that some of the challenges of development in Côte d’Ivoire, as in other developing nations, may result from a lack of socioeconomic integration capable of encouraging individual specialization, learning and interdependence, from the level of the firm to that of the nation.
We now turn the problem around and suggest that the role of mobile communications in developing societies may be changed from diagnostic to cure: If the problem is the promotion of certain kinds of social connectivity, then new uses and subscriber models in telecommunication services should help promote desirable solutions. Moreover, the interplay between observable telecommunications social connectivity patterns and economic performance is, as we showed here, observable empirically. This provides a new opportunity for creating a feedback process between experimentation of products that encourage social connectivity and performance assessment. This is, we propose, the crucial new dual role that telecommunications can play in urban (developing) societies, as both social “sensors” and “connectors”, or, put another way, as both diagnostics and potential cures.
At the national level, greater integration may be obtained by promoting better coverage and product adoption in rural areas and by attractively pricing long distance calling, especially with urban centers (Goddard and Gillespie ; Capello and Nijkamp ; Townsend ; Forestiera et al. ; The World Bank ). Economic activity could be further promoted with subscription plans that emphasize these properties targeted at businesses. Calling distant and rural areas from urban centers, and promoting urban solutions related to issues of modern technological practices in agriculture, services, telemedicine, and telebanking may help spread urban know-how to poor and remote areas. In return, primary sector increases in productivity may substitute for food and other material imports and enlarge the opportunities for exports at the urban system level (Jacobs ). Mobile phones have the potential to play a greater role in this type of economically relevant information transfer.
Inside cities, problems seem to be less predicated on the lack of overall connectivity, but rather on the promotion of its uses for more socioeconomically productive ends. A related question is how to encourage better urban services at larger scales, by exploring latent economies of scale. Calls and messaging that can convey information about urban services and help organize the public to demand their improvement could be made very inexpensive, for example. Crowd-sourced and volunteered geographic information (VGI) models for sharing information about the quality and quantity of public services can be made visible beyond the city and nation to leverage external influence to promote better organizational political and technological sustainable solutions. A system for demanding and rating the quality of public services, such as law enforcement, and to create e.g. crime hot-spot maps, that are visible not only to urbanites directly involved but to the world at large can also create a system of incentives for development. Mobile telecommunications allow each individual to be a reporter; while quality control is essential, this holds enormous possibility to bring problems to the light of day and promote coordinated larger scale solutions through political and civic organization. This bottom-up type of information transfer not only adds more eyes to gather information, but can sidestep traditional government and media outlets that may not be sufficiently lubricated to gather and let information flow quickly and freely throughout a nation.
Finally, subscriber pricing models that encourage the formation of visible and formal small firms, by shifting the structure of corporate transaction costs, may help create a culture of small formal entrepreneurship that is the basis of most job creation and innovation in developed societies (Haltiwanger et al. ). This may be achievable by lowering the costs of communication for small formal businesses with one another, and raising costs for private individuals, in relative terms, at least. The role of telecommunications in making financial transactions more transparent and formal is also an area that holds much promise in cash fund transfer models and small to medium-scale financing (Sullivan ) through the use of mobile devices, for example.