An exact algorithm for a core/periphery bipartitioning problem

The discrete optimization problem associated with partitioning a set of actors into core and periphery subsets has typically been approached using approximate procedures such as exchange heuristics, genetic algorithms, and simulated annealing. Although these procedures are effective and scalable for large networks, they do not guarantee an optimal bipartition. In this paper, an exact algorithm is presented for a core/periphery bipartitioning problem. Unlike the approximate procedures in the extant literature, this new algorithm, which is based on the principles of branch-and-bound programming, affords a guarantee of an optimal bipartition. Computational results for empirical and simulated data sets reveal that the proposed algorithm is extremely efficient for networks with 40 or fewer actors, and is often scalable for networks with up to 60 actors.     

The distant core: social solidarity,social distance and interpersonal ties in core–periphery structures

We examine three hypotheses at the foundation of theories concerned with the organization of social space and social solidarity in differentiated groups. The most important of these hypotheses is that interpersonal ties between actors in different positions of a social structure foster social solidarity; however, the theories are silent on the question of whether this effect of interpersonal ties is maintained regardless of the distance that separates the positions of two actors in the group’s social space. In addition, the current zeitgeist on the organization of social space hypothesizes that interpersonal solidarity and ties are negatively associated with the distance that separates the positions of actors in social space. Although interpersonal ties foster solidarity, social distance reduces the likelihood of interpersonal ties and solidarity. Our evidence suggests unqualified support only for the first hypothesis. Surprisingly, the expected negative effects of social distance on interpersonal ties and solidarity appear to be properties of particular forms of social organization and are not ubiquitous implications of social differentiation. These negative effects are more or less pronounced (even reversible) in core–periphery structures depending upon the distance between the core and peripheral positions in the social space of the group.     

Equicentrality and network centralization: A micro–macro linkage

This paper investigates a linkage between micro- and macrostructures as an intrinsic property of social networks. In particular, it examines the linkage between equicentrality [Kang, S.M., 2007. A note on measures of similarity based on centrality. Social Networks 29, 137–142] as a conceptualization of a microstructural process (i.e., the likelihood of social actors to be connected with similarly central others) and network centralization as a macrostructural construct, and shows that they have a negative linear association. In other words, when actors are connected with similarly central alters (i.e., high equicentrality), the overall network centralization is low. Conversely, when highly central actors are connected with low-centrality actors (i.e., low equicentrality), the overall network centralization is high. The relationship between degree equicentrality and degree centralization is more significant in observed networks, especially those evolving over time, as compared to random networks. An application of this property is given by venture capital co-investment networks.     

Computing core/periphery structures and permutation tests for social relations data

The core/periphery structure is ubiquitous in network studies. The discrete version of the concept is that individuals in a group belong to either the core, which has a high density of ties, or to the periphery, which has a low density of ties. The density of ties between the core and the periphery may be either high or low. If the core/periphery structure is given a priori, then there is no problem in finding a suitable statistical test. Often, however, the structure is not given, which presents us with two problems, searching for the optimal core/periphery structure, and devising a valid statistical test to replace the one invalidated by the search. UCINET [Borgatti, S.P., Everett, M.G., Freeman, L.C., 2002. UCINET for Windows, Version 6.59: Software for Social Network Analysis. Analytic Technologies, Harvard], the oldest and most trusted network program, gives incorrect answers in some simple cases for the first problem and does not address the second. This paper solves both problems with an adaptation of the Kernighan–Lin search algorithm, and with a permutation test incorporating this algorithm.     

Can World System Theory predict news flow on twitter? The case of government-sponsored broadcasting

Social media platforms provide world governments with the opportunity to distribute news content from their broadcast channels directly to foreign publics [Wallerstein, I. (1974). The modern world system. New York: Academic Press] World System Theory, which has successfully explained and predicted the structure of international news flow, is now being challenged. Specifically, these social platforms undermined assumptions regarding the one-way flow of information toward audiences and the exclusive institutional nature of the players in the international system. This study examines the unique case of government-sponsored news media and its international news flow. It finds that while the structure of the international news flow on Twitter exhibits a hierarchical core–periphery structure, non-institutional actors (e.g. bloggers) conformed less than institutional players (e.g. governments and news media) to that structure. This study also found that non-institutional actors assumed the role of bridging news sources and audiences, a role traditionally reserved for a small minority of elite news media. The growing and diversified pool of information mediators resulted in a more fragmented network of news flow, siloed, rather than interconnected. Research findings are synthesized and analyzed in the context of international broadcasting and social media scholarship.     

Making connections: Global Production Networks and World City Networks

This article offers a sympathetic critique of recent attempts to forge a dialogue between Global Commodity Chain (GCC) and World City Network (WCN) approaches to global economic change. While broadly supportive of the endeavour, we make three observations about this ongoing project. First, we question the utility of emphasizing the common roots of these approaches in World Systems Theory given that both have subsequently moved into new epistemological terrain and, additionally, that the language of core and periphery seems ever less pertinent to global economic realities. Second, we seek to highlight the potential dangers of essentializing the global system as one that is primarily shaped by certain kinds of connections – namely the intra-firm relationships of advanced producer service firms – between certain kinds of cities – namely the leading tiers of global cities. Third, we point to the need to expand the interpretations of relationality within global networks to include a wider variety of actors, particularly beyond the corporate realm, and to explore the dynamic power relations between those actors. We also discuss the methodological challenges of expanding the purview of research in this way. This commentary has been stimulated by the articles in the special issue of Global Networks on 'World City Networks and Global Commodity Chains'.     

Structural holes and bridging in two-mode networks

Social networks are often structured in such a way that there are gaps, or “structural holes,” between regions. Some actors are in the position to bridge or span these gaps, giving rise to individual advantages relating to brokerage, gatekeeping, access to non-redundant contacts, and control over network flows. The most widely used measures of a given actor’s bridging potential gauge the extent to which that actor is directly connected to others who are otherwise not well connected to each other. Unfortunately, the measures that have been developed to identify structural holes cannot be adapted directly to two-mode networks, like individual-to-organization networks. In two-mode networks, direct contacts cannot be directly connected to each other by definition, making the calculation of redundancy, effective size, and constraint impossible with conventional one-mode methods. We therefore describe a new framework for the measurement of bridging in two-mode networks that hinges on the mathematical concept of the intersection of sets. An actor in a given node class (“ego”) has bridging potential to the extent that s/he is connected to actors in the opposite node class that have unique profiles of connections to actors in ego’s own node class. We review the relevant literature pertaining to structural holes in two-mode networks, and we compare our primary bridging measure (effective size) to measures of bridging that result when using one-mode projections of two-mode data. We demonstrate the results of applying our approach to empirical data on the organizational affiliations of elites in a large U.S. city.     

Analysing networks of networks

We consider data with multiple observations or reports on a network in the case when these networks themselves are connected through some form of network ties. We could take the example of a cognitive social structure where there is another type of tie connecting the actors that provide the reports; or the study of interpersonal spillover effects from one cultural domain to another facilitated by the social ties. Another example is when the individual semantic structures are represented as semantic networks of a group of actors and connected through these actors’ social ties to constitute knowledge of a social group. How to jointly represent the two types of networks is not trivial as the layers and not the nodes of the layers of the reported networks are coupled through a network on the reports. We propose to transform the different multiple networks using line graphs, where actors are affiliated with ties represented as nodes, and represent the totality of the different types of ties as a multilevel network. This affords studying the associations between the social network and the reports as well as the alignment of the reports to a criterion graph. We illustrate how the procedure can be applied to studying the social construction of knowledge in local flood management groups. Here we use multilevel exponential random graph models but the representation also lends itself to stochastic actor-oriented models, multilevel blockmodels, and any model capable of handling multilevel networks.     

Policy-making on science in society between Europeanization and core–periphery divide

The aim of the paper is to identify the cross-national differences and similarities in policy-making trends on science in society (SiS) based on the comparative analysis of national reports from FP7 project “Monitoring Policy and Research Activities Related to Science in Society in Europe”. Science in society in EU is characterized by two parallel processes: Europeanization and diversity of science and innovation policies. The focus of the analysis is to explore the possible indications of Europeanization as well as diversities and find elements of certain elements of core–periphery model. The focus of the analysis is to explore the existence of common issues of SiS and on the other side different policy actions and national priorities. Although the analysis reveals the presence of Europeanization process diversities and divides are still present which draws attention to a core–periphery model. While common trends can be recognized on the theoretical and contextual level mainly coming from the various processes of Europeanization, the core–periphery model is simultaneously present on the practical level of governance and policy-making.     

Trading Blocs and the Capitalist World-Economy: Insights and Evidence

The structure of the world-economy is a central issue in world-systems research. Empirical structural analysis, however, has generally focused on a single structural aspect of the world-system: delineation of the core, periphery, and semiperiphery. This study examines another important structural facet of the world-system–blocs within the world trading order. The existence of blocs within the world-economy, as well as their configuration, have implications for states at all structural positions of the world system. Analysis of blocs which exist among core states can provide insights into issues of hegemonic cycles and decline. Outside of the core, the character of clusters can provide evidence regarding peripheral mobility, fragmentation, or subimperialism. Employing two complementary network methods, asymmetric multidimensional scaling and clique detection, this study examines blocs within the world-economy at three points since World War II: 1955, 1975, and 1994. Results indicate a somewhat multipolar, though not necessarily antagonistic, core and a somewhat fragmented periphery.     

Single-peaked Compatible Preference Profiles: Some Combinatorial Results

This paper examines combinatorial problems in connection with single-peaked preference orderings on a unidimensional scale. A binary relation, dominance, is defined on the set of connected orderings. Relevant properties of the corresponding poset and cover graph are discussed. A formula for the number of pairs of connected orderings consistent with spatial single-peakedness is derived. The total number of such pairs is shown to be expressible in a simple form involving binomial probabilities. A possible application is a coalition formation process of the kind examined by Brams et al. (J Theor Polit 14:359–383, 2002), where actors have single-peaked preferences on a common scale.     

The Cohesiveness of Blocks In Social Networks: Node Connectivity and Conditional Density

This study shows several ways that formal graph theoretic statements map patterns of network ties into substantive hypotheses about social cohesion. If network cohesion is enhanced by multiple connections between members of a group, for example, then the higher the global minimum of the number of independent paths that connect every pair of nodes in the network, the higher the social cohesion. The cohesiveness of a group is also measured by the extent to which it is not disconnected by removal of 1, 2, 3,..., k actors. Menger's Theorem proves that these two measures are equivalent. Within this graph theoretic framework, we evaluate various concepts of cohesion and establish the validity of a pair of related measures: 1. Connectivity—the minimum number k of its actors whose removal would not allow the group to remain connected or would reduce the group to but a single member—measures the social cohesion of a group at a general level. 2. Conditional density measures cohesion on a finer scale as a proportion of ties beyond that required for connectivity k over the number of ties that would force it to k + 1.
Calibrated for successive values of k, these two measures combine into an aggregate measure of social cohesion, suitable for both small- and large-scale network studies. Using these measures to define the core of a new methodology of cohesive blocking, we offer hypotheses about the consequences of cohesive blocks for social groups and their members, and explore empirical examples that illustrate the significance, theoretical relevance, and predictiveness of cohesive blocking in a variety of substantively important applications in sociology.     

Needs for rural research in the northern Finland context

The aim of this paper is to discuss the needs and demands which rural research faces at the interface between research and development. The case study area is northern Finland, which constitutes the most remote and sparsely populated areas of the European Union. This paper is based on the tradition of rural research since the 1980s in connection with the development of programme-based rural and regional policy. Rural researchers are desired actors in rural and regional development projects and programmes both at the national and regional level, but their challenge is to fulfil both academic standards of their background research organization and the often very practical needs of local and regional rural development actors. According to the opinions of rural actors in northern Finland, the definition of rural research is somewhat unclear and multidisciplinarity of rural research seems to give a free hand to carry out many kinds of research under the title. The needs and demand for rural research(ers) are quite practical and are mostly connected to the creation of new job opportunities outside primary production and development of villages via proposals given by researchers. The major result of this study is that rural research is highly appreciated both in programmes and among actors on the “field”, although the real role given to research remains unclear in most cases.     

Power and its sources in the governance of global value chains: The Argentina–European Union biodiesel value chain

This paper tackles the broader question of why inequality along global value chains (GVCs) tends to remain unchallenged despite the successful upgrading and insertion of firms operating in the world-system's periphery. Because the reduction and reproduction of inequalities are both intimately connected to power relations along GVCs, such relations are at the core of my analysis. Conceptually, my theorization of power builds on recent work by Dallas, Ponte and Sturgeon, which has sought to more systematically theorize and account for the multidimensional nature of power, and complements it with key insights drawn from World-Systems theory. Empirically, this paper analyses the biodiesel GVC between Argentina and the European Union, a case in which the successful economic upgrading and enhanced competitiveness of biodiesel producers in Argentina fail to overturn their subordinated position vis-à-vis European producers and traders.     

Impacts of domestic population dynamics and foreign wood trade on deforestation: a world-system perspective

World system theory posits that core nations control global production processes through their economic and political-military strength, while countries at the periphery remain technologically underdeveloped and operate from a position of dependency. Rapid changes such as population growth and rural encroachment have spurred environmental degradation in the intermediary semi-periphery countries. The effects of world system structure on national deforestation were investigated in a quantitative, cross-national analysis of data from 60 core, semi-peripheral, and peripheral countries. This analysis revealed that rural population growth has had a deleterious effect on forestation throughout the world system. However, the impact of general population growth has been negative only in non-core countries. As hypothesized, forest exports have resulted in ecologic devastation in the periphery of the world system, but have exerted a favorable effect for core countries where reforestation programs dominate. These findings suggest that population growth per se is not the critical factor in environmental degradation. Urged are further quantitative evaluations of the environmental impact of other international commodity trades.     

NATION-STATES CONFRONT THE GLOBAL: Discourses of Indigenous Rights in Fiji and Tanzania

How do global issue constructions serve as resources for actors engaged in domestic political contention, and what does the appropriation of global ideas by domestic actors imply about the spread of global culture? To contribute to knowledge about conflict‐based diffusion of global ideas, we examine the histories of global constructions of indigenous rights and national debates about indigenous rights in Fiji and Tanzania. While global models of indigenous rights emphasize self‐determination for nondominant, culturally distinct groups at risk from the nation‐state, advocates for indigenization policies in Fiji and Tanzania have argued for state policies to entrench political and economic rights for majority or near‐majority groups that were well integrated into the nation‐state. Although transnationally connected indigenous rights organizations have a greater presence in Tanzania than in Fiji, actors in Fiji remain more engaged with changes in international indigenous rights discourse than their counterparts in Tanzania. This difference reflects variations in the leverage global culture offered in the two cases because of its externality to national political debates. In Fiji, actors appropriated global culture as a means to internationalize a domestic dispute, while in Tanzania the impetus for indigenization came from global economic pressures. Our findings imply that conflict‐based diffusion concentrates agency with respect to the use of global legal discourses in domestic actors rather than the globally connected actors and experts who carry global culture in consensus‐based diffusion.     

广东省新兴产业园区的土地集约化利用比较研究——基于增城汽车产业核心区与河源高新区的调查分析

改革开放30余年的发展使广东省形成了以珠三角地区为核心、以东西两翼和北部山区为外围的核心一外围圈层格局,近年来广东省经济发展进入新的增长阶段,在核心和外围圈层表现出不同的特征。本文通过位于核心圈层的增城汽车核心产业区与位于外围圈层的河源高新区的比较,研究了两大圈层产业园区在土地集约化利用上的差别。研究表明：核心圈层产业园区在产业结构上表现出大型企业主导的专业化发展特征,外围圈层产业园区则表现出中小型企业主导的多样化发展特征;核心圈层产业园区的经济增长模式表现出重大项目带动的特征,外围圈层产业园区则表现出基础设施驱动的特征;核心圈层的产业园区土地开发效益表现出高投入高产出高回报的特点,外围圈层的产业园区则表现出低投入低产出低回报的特点;最后,文章在两者的比较研究基础上提出了广东省新兴产业园区发展的几点建议。     

Colonizing nature: scientific knowledge, colonial power and the incorporation of India into the modern world-system

In this paper, the role of scientific knowledge, institutions and colonialism in mutually co-producing each other is analysed. Under the overarching rubric of colonial structures and imperatives, amateur scientists sought to deploy scientific expertise to expand the empire while at the same time seeking to take advantage of the opportunities to develop their careers as 'scientists'. The role of a complex interplay of structure and agency in the development of modern science, not just in India but in Britain too is analysed. The role of science and technology in the incorporation of South Asian into the modern world system, as well as the consequences of the emergent structures in understanding the trajectory of modern science in post-colonial India is examined. Overall, colonial rule did not simply diffuse modern science from the core to the periphery. Rather the colonial encounter led to the development of new forms of scientific knowledge and institutions both in the periphery and the core.     

Finding the Homosexual in Women’s Rights

In recent years, organizations on the American Christian Right (CR) have become established actors at the United Nations, working to limit international agreement on developments seen as ‘anti-family’, such as women’s rights, population policy and abortion. At the same time, the Vatican has established itself as a strong voice opposing international law and policy on women’s rights. For both actors, women’s rights represent a direct challenge to the ‘natural family’ and hence a particular world vision premised on a sexual division of labour. While women’s rights is a central preoccupation for both actors, ‘homosexuality’ and the prospect of lesbian and gay rights and ‘gay marriage’ is also a recurrent theme, intricately connected to women’s rights. This article explores the relationship between women’s rights and homosexuality as drawn by these two actors. It asks why, in an international arena that offers little concrete recognition of, or protection for, lesbian and gay identities both the CR and Vatican are concerned about a presumed homosexual agenda. It also explores what role the debate about women’s rights plays in facilitating this ‘homosexual agenda’. In addressing these questions, this article seeks to explore, and raise further questions about international women’s rights as a language for international discussion about social relations.     

How stable is the core discussion network?

Researchers have paid increasing attention to the core discussion network, the set of people we turn to when discussing important matters. Because the core discussion network is theorized to be composed of people's closest ties, not fleeting acquaintances, it is expected to be largely stable, evolving slowly over the span of people's lives. However, recent studies have shown that networks are strongly affected by the contexts in which people interact with others, and as people experience life course transitions, they also often enter new contexts – school, college, work, marriage, and retirement. We ask whether, as actors enter new social contexts, the core discussion network remains stable or changes rapidly. Based on original, longitudinal, qualitative and quantitative data on the experience of first-year graduate students in three academic departments in a large university, we examine the stability of the core discussion network over the first 6 and 12 months in this new context. We test four competing hypotheses that focus on strength of ties, new opportunities, obligations, and routine activity and predict, respectively, stasis, expansion, shedding, and substitution. We find that the core discussion network changes remarkably quickly, with little or no lag, and that it appears to do so because both the obligations that people face and the routine activities they engage in are transformed by new institutional environments. Findings suggest that core discussion network may be less a “core” network than a highly contextual support network in which people are added and dropped as actors shift from environment to environment.