Publications

Abstract:

This book summarizes our work in networks and economic development, introduce the concept of personbyte and provides growth predictions for the year 2020. Download Book

Abstract:

Much of the analysis of economic growth has focused on the study of aggregate output. Here, we deviate from this tradition and look instead at the structure of output embodied in the network connecting countries to the products that they export.We characterize this network using four structural features: the negative relationship between the diversification of a country and the average ubiquity of its exports, and the non-normal distributions for product ubiquity, country diversification and product co-export. We model the structure of the network by assuming that products require a large number of non-tradable inputs, or capabilities, and that countries differ in the completeness of the set of capabilities they have. We solve the model assuming that the probability that a country has a capability and that a product requires a capability are constant and calibrate it to the data to find that it accounts well for all of the network features except for the heterogeneity in the distribution of country diversification. In the light of the model, this is evidence of a large heterogeneity in the distribution of capabilities across countries. Finally, we show that the model implies that the increase in diversification that is expected from the accumulation of a small number of capabilities is small for countries that have a few of them and large for those with many. This implies that the forces that help drive divergence in product diversity increase with the complexity of the global economy when capabilities travel poorly. Download Paper

Abstract:

What are Southern and East Africa’s industrial opportunities? In this article the author explores this question by using the product space to study the productive structure of five Southern and East African countries: Kenya, Mozambique, Rwanda, Tanzania, and Zambia. The product space is a network connecting products that tend to be exported by the same sets of countries. Since countries are more likely to develop products that are close by in the product space to the ones that they already produce, the product space can be used to help anticipate a country’s industrial opportunities.

The results suggest that the most natural avenue for future product diversification for these five Southern and East African nations resides in the agricultural sector, since all of these nations appear to have productive structures that are pre-adapted to the production of many agricultural products that none of them are currently exporting.

The author concludes this paper by exploring the potential benefits of further regional economic integration through an exercise in which he pulled together the productive structures of these five countries. This exercise shows that the products that become more accessible in the combined economy are once again predominantly agricultural. These results suggest that while diversification into all sectors should remain an important long-term goal of the region, the path towards increased diversification in the near future may well lie in a more empowered and diverse agricultural sector.

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Abstract:

Countries differ markedly in the diversification of their exports. Products differ in the number of countries that export them, which we define as their ubiquity. We document a new stylized fact in the global pattern of exports: there is a systematic relationship between the diversification of a country’s exports and the ubiquity of its products. We argue that this fact is not implied by current theories of international trade and show that it is not a trivial consequence of the heterogeneity in the level of diversification of countries or of the heterogeneity in the ubiquity of products. We account for this stylized fact by constructing a simple model that assumes that each product requires a potentially large number of non-tradable inputs, which we call capabilities, and that a country can only make the products for which it has all the requisite capabilities. Products differ in the number and specific nature of the capabilities they require, as countries differ in the number/nature of capabilities they have. Products that require more capabilities will be accessible to fewer countries (i.e., will be less ubiquitous), while countries that have more capabilities will have what is required to make more products (i.e., will be more diversified). Our model implies that the return to the accumulation of new capabilities increases exponentially with the number of capabilities already available in a country. Moreover, we find that the convexity of the increase in diversification associated with the accumulation of a new capability increases when either the total number of capabilities that exist in the world increases or the average complexity of products, defined as the number of capabilities products require, increases. This convexity defines what we term as a quiescence trap, or a trap of economic stasis: countries with few capabilities will have negligible or no return to the accumulation of more capabilities, while at the same time countries with many capabilities will experience large returns – in terms of increased diversification – to the accumulation of additional capabilities. We calibrate the model to three different sets of empirical data and show that the derived functional forms reproduce the empirically observed distributions of product ubiquity, the relationship between the diversification of countries and the average ubiquity of the products they export, and the distribution of the probability that two products are co-exported. This calibration suggests that the global economy is composed of a relatively large number of capabilities – between 23 and 80, depending on the level of disaggregation of the data – and that products require on average a relatively large fraction of these capabilities in order to be produced. The conclusion of this calibration is that the world exists in a regime where the quiescence trap is strong.
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Abstract:

In this paper we introduce five graphical statistical methods to compare countries level of development relative to other countries and across time. For this, we use seven panels of data on the Human Development Index and its components, containing information on more than 100 countries for more than 35 years. We create visual comparisons of the level of development of countries relative to each other, and across time, through five different visualization techniques: (i) Rankings (ii) Values (iii) Distributions (iv) visual metaphors (The Development Tree), and (v) networks, by introducing the concepts of Partial Ordering Networks (PON) and Development Reference Groups (DRG). The graphical exploration of both, values and distributions, show a saturation of both the education and life dimensions of the HDI, suggesting a need to extend the definitions of this components to include either more subcomponents, or completely new measures that could help differentiate between countries facing different development challenges. The Development Tree and the Partial Ordering Network, on the other hand, are used to create graphical narratives of countries and regions. The simplicity of the Development Tree makes it an ideal graphical metaphor for branding the HDI in a multilingual setting, whereas Partial Ordering Networks provide a more organic way to group countries according to their levels of development and connect countries to those with similar development challenges. We conclude by arguing that graphical statistical methods could be used to help communicate complex data and concepts through universal cognitive channels that are heretofore underused in the development literature. Download Paper

Abstract:

This book chapter summarizes some literature on networks and complexity science for a management audience. Download Paper

Abstract:

How does the productive structure of countries’ changes over time? In this paper we explore this question by combining techniques of networks science with 42 years of trade data and find that, while the Product Space remains relatively stable during this period, the dynamics of countries’ productive structures is characterized by a few highly dynamic economies. In particular we identify Brazil, Indonesia, Turkey, Malaysia, Thailand, Korea, Singapore and China, as countries that transformed their productive structures considerably during these four decades, albeit following different trajectories. For instance, the economic complexity of Korea, Singapore and China was relatively high at the beginning of the observation period and continued to increase during these forty two years, moving these countries into the top spots of the economic complexity rankings for the beginning of this millennium. Brazil, Indonesia and Turkey, on the other hand, transformed their productive structures significantly during the same period of time, but did so starting from a less sophisticated foundation. We conclude the paper by moving from this and other observations into the policy implications of this view of economic development and argue that the government involvement in the private sector should be to help catalyze market activities and solve coordination problems that emerge naturally when countries try to accumulate capabilities. This represents an alternative to more traditional views of the role of government that postulate, in their extremes, that the public sector should either have no involvement in private sector activities or, on the other hand, substantial ownership of the means of production. Download Paper

Abstract:

For Adam Smith, wealth was related to the division of labor. As people and firms specialize in different activities, economic efficiency increases, suggesting that development is associated with an increase in the number of individual activities and with the complexity that emerges from the interactions between them. Here we develop a view of economic growth and development that gives a central role to the complexity of a country’s economy by interpreting trade data as a bipartite network in which countries are connected to the products they export, and show that it is possible to quantify the complexity of a country’s economy by characterizing the structure of this network. Furthermore, we show that the measures of complexity we derive are correlated with a country’s level of income, and that deviations from this relationship are predictive of future growth. This suggests that countries tend to converge to the level of income dictated by the complexity of their productive structures, indicating that development efforts should focus on generating the conditions that would allow complexity to emerge to generate sustained growth and prosperity.
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Abstract:

We modeled the mobility of mobile phone users in order to study the fundamental spreading patterns that characterize a mobile virus outbreak. We find that although Bluetooth viruses can reach all susceptible handsets with time, they spread slowly because of human mobility, offering ample opportunities to deploy antiviral software. In contrast, viruses using multimedia messaging services could infect all users in hours, but currently a phase transition on the underlying call graph limits them to only a small fraction of the susceptible users. These results explain the lack of a major mobile virus breakout so far and predict that once a mobile operating system’s market share reaches the phase transition point, viruses will pose a serious threat to mobile communications. Download Paper Project Website

Abstract:

The use of networks to integrate different genetic, proteomic, and metabolic datasets has been proposed as a viable path toward elucidating the origins of specific diseases. Here we introduce a new phenotypic database summarizing correlations obtained from the disease history of more than 30 million patients in a Phenotypic Disease Network (PDN). We present evidence that the structure of the PDN is relevant to the understanding of illness progression by showing that (1) patients develop diseases close in the network to those they already have; (2) the progression of disease along the links of the network is different for patients of different genders and ethnicities; (3) patients diagnosed with diseases which are more highly connected in the PDN tend to die sooner than those affected by less connected diseases; and (4) diseases that tend to be preceded by others in the PDN tend to be more connected than diseases that precede other illnesses, and are associated with higher degrees of mortality. Our findings show that disease progression can be represented and studied using network methods, offering the potential to enhance our understanding of the origin and evolution of human diseases. The dataset introduced here, released concurrently with this publication, represents the largest relational phenotypic resource publicly available to the research community.

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Abstract:

The discovery that many complex systems are actually well-structured networks has not only changed the landscape of physics, but also how we visualize patterns in science, explains César A Hidalgo Download Paper

Abstract:

Does the type of product a country exports matter for subsequent economic performance? to take an example from the 19th-century economist David ricardo, does it matter if Britain specializes in cloth and portugal in wine for the subsequent development of either country? the seminal texts of development economics held that it does matter, suggesting that industrialization creates externalities that lead to accelerated growth (rosenstein-rodan 1943; Hirschman 1958; Matsuyama 1992). Yet, lacking formal models, mainstream economic theory has made little of these ideas. instead, current dominant theories use two approaches to explain countries’ patterns of specialization.

The first approach focuses on the relative proportions in which countries possess productive factors (physical capital, labor, land, skills or human capital, infrastructure, and institutions) and the proportions in which these factors are needed to produce different goods (see Flam and Flanders 1991). Hence, poor countries specialize in goods that are relatively intensive in labor and land, while richer countries specialize in goods that use more human and physical capital and demand better infrastructure and institutions. According to these… (read more by downloading paper)

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Abstract:

Despite their importance for urban planning, traffic forecasting, and the spread of biological and mobile viruses, our understanding of the basic laws governing human motion remains limited owing to the lack of tools to monitor the time-resolved location of individuals. Here we study the trajectory of 100,000 anonymized mobile phone users whose position is tracked for a six-month period. We find that, in contrast with the random trajectories predicted by the prevailing Le´vy flight and random walk models, human trajectories show a high degree of temporal and spatial regularity, each individual being characterized by a timeindependent characteristic travel distance and a significant probability to return to a few highly frequented locations. After correcting for differences in travel distances and the inherent anisotropy of each trajectory, the individual travel patterns collapse into a single spatial probability distribution, indicating that, despite the diversity of their travel history, humans follow simple reproducible patterns. This inherent similarity in travel patterns could impact all phenomena driven by human mobility, from epidemic prevention to emergency response, urban planning and agent-based modelling. Download Paper Project Website

Abstract:

The empirical study of network dynamics has been limited by the lack of longitudinal data. Here we introduce a quantitative indicator of link persistence to explore the correlations between the structure of a mobile phone network and the persistence of its links.We show that persistent links tend to be reciprocal and are more common for people with low degree and high clustering. We study the redundancy of the associations between persistence, degree, clustering and reciprocity and show that reciprocity is the strongest predictor of tie persistence. The method presented can be easily adapted to characterize the dynamics of other networks and can be used to identify the links that are most likely to survive in the future Download Paper

Abstract:

Economies grow by upgrading the products they produce and export. The technology, capital, institutions, and skills needed to make newer products are more easily adapted from some products than from others. Here, we study this network of relatedness between products, or “product space,” finding that more-sophisticated products are located in a densely connected core whereas less sophisticated products occupy a less-connected periphery. Empirically, countries move through the product space by developing goods close to those they currently produce. Most countries can reach the core only by traversing empirically infrequent distances, which may help explain why poor countries have trouble developing more competitive exports and fail to converge to the income levels of rich countries.

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Abstract:

Transcription regulatory networks play a pivotal role in the development, function, and pathology of metazoan organisms. Such networks are comprised of protein–DNA interactions between transcription factors (TFs) and their target genes. An important question pertains to how the architecture of such networks relates to network functionality. Here, we show that a Caenorhabditis elegans core neuronal protein–DNA interaction network is organized into two TF modules. These modules contain TFs that bind to a relatively small number of target genes and are more systems specific than the TF hubs that connect the modules. Each module relates to different functional aspects of the network. One module contains TFs involved in reproduction and target genes that are expressed in neurons as well as in other tissues. The second module is enriched for paired homeodomain TFs and connects to target genes that are often exclusively neuronal. We find that paired homeodomain TFs are specifically expressed in C. elegans and mouse neurons, indicating that the neuronal function of paired homeodomains is evolutionarily conserved. Taken together, we show that a core neuronal C. elegans protein–DNA interaction network possesses TF modules that relate to different functional aspects of the complete network. Download Paper

Abstract:

Differential regulation of gene expression is essential for cell fate specification in metazoans. Characterizing the transcriptional activity of gene promoters, in time and in space, is therefore a critical step toward understanding complex biological systems. Here we present an in vivo spatiotemporal analysis for B900 predicted C. elegans promoters (B5% of the predicted proteincoding genes), each driving the expression of green fluorescent protein (GFP). Using a flow-cytometer adapted for nematode profiling, we generated ‘chronograms’, two-dimensional representations of fluorescence intensity along the body axis and throughout development from early larvae to adults. Automated comparison and clustering of the obtained in vivo expression patterns show that genes coexpressed in space and time tend to belong to common functional categories. Moreover, integration of this data set with C. elegans protein-protein interactome data sets enables prediction of anatomical and temporal interaction territories between protein partners. Download Paper

Abstract:

We develop a ‘basic principles’modelwhich accounts for the primary life cycle consumption of films as a social coordination problem in which information transmission is governed by word of mouth. We fit the analytical solution of such a model to aggregated consumption data from the film industry and derive a quantitative estimator of its quality based on the structure of the life cycle. Download Paper

Abstract:

Inter-event times have been studied across various disciplines in search for correlations. In this paper, we show analytical and numerical evidence that at the population level a power-law can be obtained by assuming Poissonian agents with different characteristic times, and at the individual level by assuming Poissonian agents that change the rates at which they perform an event in a random or deterministic fashion. The range in which we expect to see this behavior and the possible deviations from it are studied by considering the shape of the rate distribution. Download Paper

Abstract:

An analytical approach to network dynamics is used to show that when agents copy their state randomly, the network arrives to a stationary regime in which the distribution of states is independent of the degree. The effects of network topology on the process are characterized introducing a quantity called influence and studying its behavior for scale-free and random networks. We show that for this model degree averaged quantities are constant in time regardless of the number of states involved. Download Paper

Abstract:

En este trabajo analizamos la situación docente actual en las áreas de Biología, Física y Química en enseñanza media. Demostramos que existe un déficit de profesores con estudios actualmente vigentes en la especialidad, que afecta en forma desigual a las tres ciencias. Concluimos que se requieren enérgicas medidas de estímulo en el sector para hacer viable la implementación satisfactoria y con equidad de los programas de estudio. Download Paper