nep-net New Economics Papers
on Network Economics
Issue of 2021‒04‒19
seventeen papers chosen by
Alfonso Rosa García
Universidad de Murcia

  1. Integration and Diversity By Sanjeev Goyal; Penélope Hernández; Guillem Martínez-Cánovas; Frederic Moisan; Manuel Muñoz-Herrera; Angel Sánchez
  2. Effect of Network Topology and Node Centrality on Trading By Felipe Maciel Cardoso; Carlos Gracia-Lázaro; Frederic Moisan; Sanjeev Goyal; Angel Sánchez; Yamir Moreno
  3. Ethnic Mixing in Early Childhood: Evidence from a Randomized Field Experiment and a Structural Model By Boucher, Vincent; Tumen, Semih; Vlassopoulos, Michael; Wahba, Jackline; Zenou, Yves
  4. Attack and Interception in Networks By Francis Bloch; Kalyan Chatterjee; Bhaskar Dutta
  5. Uncovering seeds By Ballester, Coralio; Vorsatz, Marc; Ponti, Giovanni
  6. A Network Solution to Robust Implementation: The Case of Identical but Unknown Distributions By Mariann Ollar; Antonio Penta
  7. Endogenous Information Sharing and the Gains from Using Network Information to Maximize Technology Adoption By Dar, Manzoor H.; de Janvry, Alain; Emerick, Kyle; Kelley, Erin M.; Sadoulet, Elisabeth
  8. Earnings Inequality in Production Networks By Federico Huneeus; Kory Kroft; Kevin Lim
  9. Comparative statics and centrality measures in oligopolies with interdependent preferences By Marco F. Boretto; Fausto Cavalli; Ahmad Naimzada
  10. Loss of structural balance in stock markets By E. Ferreira; S. Orbe; J. Ascorbebeitia; B. \'Alvarez Pereira; E. Estrada
  11. Tree Networks to assess Financial Contagion By Agosto, Arianna; Ahelegbey, Daniel Felix; Giudici, Paolo
  12. Resource Availability in the Social Cloud: An Economics Perspective By Pramod C. Mane; Nagarajan Krishnamurthy; Kapil Ahuja
  13. The dawn of a mobile payment scheme: The case of Movii By Carlos León
  14. Who Drives if No-one Governs? A Social Network Analysis of Social Protection Policy in Madagascar By Katya Long; Jean-Philippe Berrou; Alain Piveteau; Thibaud Deguilhem; Leo Delpy; Claire Gondard-Delcroix
  15. Network-centric indicators for fragility in global financial indices By Areejit Samal; Sunil Kumar; Yasharth Yadav; Anirban Chakraborti
  16. Homophily, Peer Effects, and Dishonesty By Liza Charroin; Bernard Fortin; Marie Claire Villeval
  17. Rapid detection of fast innovation under the pressure of COVID-19 By Nicola Melluso; Andrea Bonaccorsi; Filippo Chiarello; Gualtiero Fantoni

  1. By: Sanjeev Goyal (emlyon business school); Penélope Hernández; Guillem Martínez-Cánovas; Frederic Moisan; Manuel Muñoz-Herrera; Angel Sánchez
    Abstract: We study a setting where individuals prefer to coordinate with others but they differ on their preferred action. Our interest is in understanding the role of link formation with others in shaping behavior. So we consider the situation in which interactions are exogenous and a situation where individuals choose links that determine the interactions. Theory is permissive in both settings: conformity (on either of the actions) and diversity (with different groups choosing their preferred actions) are both sustainable in equilibrium. We conduct an experiment to understand how link formation affects equilibrium selection. Our experiment reveals the powerful effect of linking on equilibrium selection: with an exogenous complete network, subjects choose to conform on the majority's preferred action. By contrast, with endogenous linking—irrespective of the costs of linking—subjects always opt for diversity of actions.
    Keywords: networks,equilibrium selection,Social coordination,experiment
    Date: 2020–09–10
  2. By: Felipe Maciel Cardoso (emlyon business school); Carlos Gracia-Lázaro; Frederic Moisan; Sanjeev Goyal; Angel Sánchez; Yamir Moreno
    Abstract: Global supply networks in agriculture, manufacturing, and services are a defining feature of the modern world. The efficiency and the distribution of surpluses across different parts of these networks depend on the choices of intermediaries. This paper conducts price formation experiments with human subjects located in large complex networks to develop a better understanding of the principles governing behavior. Our first experimental finding is that prices are larger and that trade is significantly less efficient in small-world networks as compared to random networks. Our second experimental finding is that location within a network is not an important determinant of pricing. An examination of the price dynamics suggests that traders on cheapest—and hence active—paths raise prices while those off these paths lower them. We construct an agent-based model (ABM) that embodies this rule of thumb. Simulations of this ABM yield macroscopic patterns consistent with the experimental findings. Finally, we extrapolate the ABM on to significantly larger random and small-world networks and find that network topology remains a key determinant of pricing and efficiency.
    Date: 2020–07–06
  3. By: Boucher, Vincent (Université Laval); Tumen, Semih (TED University); Vlassopoulos, Michael (University of Southampton); Wahba, Jackline (University of Southampton); Zenou, Yves (Monash University)
    Abstract: We study the social integration of ethnic minority children in the context of an early childhood program conducted in Turkey aimed at preparing 5-year-old native and Syrian refugee children for primary school. We randomly assign children to groups with varying ethnic composition and find that exposure to children of the other ethnicity leads to an increase in the formation of interethnic friendships, especially for Turkish children. We also find that the Turkish language skills of Syrian children are better developed in classes with a larger presence of Turkish children. We then develop a model of friendship formation with two key mechanisms: preference bias and congestion in the friendship formation process. Structural estimation of the model suggests that interethnic exposure reduces the share of own-ethnicity friends (homophily) and has a non-monotonic effect on the propensity to form own-ethnicity friendships beyond what would be expected given the size of the group (inbreeding homophily). Counterfactual analysis indicates that improvement in the language skills of Syrian children can offset more than half of the effect that ethnic bias has on friendship formation patterns. Finally, we find that for Syrian children exposure to Turkish children in the pre-school program has a long-term effect on primary school absenteeism.
    Keywords: refugees, early childhood, randomized field experiment, structural estimation, network formation, non-cognitive skills
    JEL: D85 J15 J18 Z13
    Date: 2021–04
  4. By: Francis Bloch (Paris School of Economics); Kalyan Chatterjee (Pennsylvania State University); Bhaskar Dutta (Ashoka University)
    Abstract: This paper studies a game of attack and interception in a network, where a single attacker chooses a target and a path, and each node chooses a level of protection. We show that the Nash equilibrium of the game exists and is unique. It involves a mixed strategy of the attacker except when one target has a very high value relative to others. We characterize equilibrium attack paths and attack distributions as a function of the underlying network and target values. We also show that adding a link or increasing the value of a target may harm the attacker - a comparative statics effect which is reminiscent of Braess's paradox in transportation economics. Finally, we contrast the Nash equilibrium with the equilibria of two variations of the model: one where nodes make sequential protection decisions upon observing the arrival of a suspicious object, and one where all nodes cooperate in defense.
    Keywords: Network interdiction, Networks, Attack and defense, Inspection
    Date: 2021–04
  5. By: Ballester, Coralio; Vorsatz, Marc; Ponti, Giovanni
    Abstract: We provide the theoretical foundations for a new estimation algorithm that non-parametrically infers level-k beliefs from laboratory choices in generalized guessing games with heterogeneous interactions. The algorithm takes the strategic dependencies of the game and subjects' choices as an input and returns a detailed histogram (a ``pseudo-spectrogram'' of seeds) that represents population beliefs about the behavior of level-0 players. As a by-product, the algorithm also returns the estimated population composition of reasoning levels. The main contributions are as follows. First, we study the equilibrium properties of generalized guessing games and provide an ordinal (visual) characterization for uniqueness. Second, within the level-k model, our key theoretical results establish conditions on the subjective beliefs or the game structure so that the population distributions of level-k choices and the population distribution of beliefs are alike. These results are obtained without any distributional assumptions. We also present a central limit result that supports the use of parametric gaussian approaches often used in the literature. Third, on the basis of the theoretical results, we construct a new a non-parametric maximum likelihood estimation algorithm that fully identifies the belief pattern. Fourth, we apply the algorithm to experimental data. It is found that beliefs cluster around a few focal points and that a few seeds are able to explain a high percentage of observed behavior. Finally, our theoretical results can also be useful in the design of laboratory guessing games with good estimation properties.
    Keywords: beliefs, estimation, level-k, network, mixture model.
    JEL: C13 C72 C87 C90 C92 D01
    Date: 2021–04–11
  6. By: Mariann Ollar; Antonio Penta
    Abstract: We consider mechanism design environments in which agents commonly know that others’ types are identically distributed, but without assuming that the actual distribution is common knowledge, nor that it is known to the designer (common knowledge of identicality, CKI). Under these assumptions, we study problems of partial and full implementation, as well as robustness. First, we characterize the transfers which are incentive compatible under the CKI assumption, and provide necessary and sufficient conditions for partial implementation. Second, we characterize the conditions under which full implementation is possible via direct mechanisms, as well as the transfer schemes which achieve full implementation whenever it is possible. We do this by pursuing a network approach, which is based on the observation that the full implementation problem in our setting can be conveniently transformed into one of designing a network of strategic externalities, subject to suitable constraints which are dictated by the incentive compatibility requirements entailed by the CKI assumption. This approach enables us to uncover a fairly surprising result: the possibility of full implementation is characterized by the strength of the preference interdependence of the two agents with the least amount of preference interdependence, regardless of the total number of agents, and of their preferences. Finally, we study the robustness properties of the implementing transfers with respect to both misspecifications of agents’ preferences and with respect to lower orders beliefs in rationality.
    Keywords: moment conditions, robust full implementation, Rationalizability, interdependent values, identical but unknown distributions, uniqueness, strategic externalities, spectral radius, canonical transfers, loading transfers, equal-externality transfers
    JEL: D62 D82 D83
    Date: 2021–04
  7. By: Dar, Manzoor H.; de Janvry, Alain; Emerick, Kyle; Kelley, Erin M.; Sadoulet, Elisabeth
    Abstract: Can agents in a social network be induced to obtain information from outside their peer groups? Using a field experiment in rural Bangladesh, we show that demonstration plots in agriculture - a technique where the first users of a new variety cultivate it in a side-by-side comparison with an existing variety - facilitate social learning by inducing conversations and information sharing outside of existing social networks. We compare these improvements in learning with those from seeding new technology with more central farmers in village social networks. The demonstration plots - when cultivated by randomly selected farmers - improve knowledge by just as much as seeding with more central farmers. Moreover, the demonstration plots only induce conversations and facilitate learning for farmers that were unconnected to entry points at baseline. Finally, we combine this diffusion experiment with an impact experiment to show that both demonstration plots and improved seeding transmit information to farmers that are less likely to benefit from the new innovation.
    Keywords: Social and Behavioral Sciences
    Date: 2019–05–29
  8. By: Federico Huneeus; Kory Kroft; Kevin Lim
    Abstract: This paper investigates the importance of firm-to-firm production network linkages for earnings inequality. We develop a quantitative model in which heterogeneous firms hire workers of different abilities in an imperfectly competitive labor market and source intermediates from heterogeneous suppliers in a production network. The model delivers an earnings equation with a firm-specific wage premium that depends endogenously on both firm productivities and firm-to-firm linkages in the production network. We establish identification of the model parameters and estimate them using linked employer-employee and firm-to-firm transactions data from Chile. Counterfactual simulations using our estimated model show that heterogeneity in network linkages explains 21% of log earnings variance, while passthrough of productivity shocks via network linkages explains between 20-25% of earnings volatility. We also examine the effects of a minimum wage policy and find strong spillover effects to worker earnings above the wage floor, with substitution of materials for labor explaining around 40% of these effects.
    Date: 2021–03
  9. By: Marco F. Boretto; Fausto Cavalli; Ahmad Naimzada
    Abstract: Considering the Cournot oligopoly with interdependent preferences proposed in [5], we analyze the effects of a change in the network of social interactions. Reconsidering some of the main centrality measures proposed in the literature, we show how intercentrality, Bonacich and Friedkin-Johnsen centrality measures can be related in a network described by a general matrix of interaction. This allows showing under what conditions a firm can benefit, in terms of equilibrium performance, from a change in the weight of interaction with respect to one of its competitors. Extending the approach to the study of a uniform change in the behavior of all the firms, we show that it is collectively beneficial only if the structure of social interaction is characterized by a sufficient degree of homogeneity in terms of weight distributions.
    Keywords: Cournot Game, Preference interdependence, Network, Centrality measures, Comparative statics.
    JEL: D43 C62 C70
    Date: 2021–03
  10. By: E. Ferreira (Department of Quantitative Methods, University of the Basque Country UPV/EHU); S. Orbe (Department of Quantitative Methods, University of the Basque Country UPV/EHU); J. Ascorbebeitia (Department of Economic Analysis, University of the Basque Country UPV/EHU); B. \'Alvarez Pereira (Nova School of Business and Economics); E. Estrada (Institute of Mathematics and Applications, University of Zaragoza, ARAID Foundation. Institute for Cross-Disciplinary Physics and Complex Systems)
    Abstract: We use rank correlations as distance functions to establish the interconnectivity between stock returns, building weighted signed networks for the stocks of seven European countries, the US and Japan. We establish the theoretical relationship between the level of balance in a network and stock predictability, studying its evolution from 2005 to the third quarter of 2020. We find a clear balance-unbalance transition for six of the nine countries, following the August 2011 Black Monday in the US, when the Economic Policy Uncertainty index for this country reached its highest monthly level before the COVID-19 crisis. This sudden loss of balance is mainly caused by a reorganization of the market networks triggered by a group of low capitalization stocks belonging to the non-financial sector. After the transition, the stocks of companies in these groups become all negatively correlated between them and with most of the rest of the stocks in the market. The implied change in the network topology is directly related to a decrease in stocks predictability, a finding with novel important implications for asset allocation and portfolio hedging strategies.
    Date: 2021–04
  11. By: Agosto, Arianna; Ahelegbey, Daniel Felix; Giudici, Paolo
    Abstract: We propose a two-layered tree network model that decomposes financial contagion into a global component, composed of inter-country contagion effects, and a local component, made up of inter-institutional contagion channels. The model is effectively applied to a database containing time series of daily CDS spreads of major European financial institutions (banks and insurance companies), and reveals the importance of monitoring both channels to assess financial contagion. Our empirical application reveals evidence of a high inter-country and inter-institutional vulnerability at the onset of the global financial crisis in 2008 and during the sovereign crisis in 2011. The results identify France as central to the inter-country contagion in the Euro area during the financial crisis, while Italy dominates during the sovereign crisis. The application of the model to detect contagion between sectors of the European economy reveals similar findings, and identifies the manufacturing sector as the most central, while, at the company level, financial institutions dominate during the 2008 crisis.
    Keywords: Financial crisis; Graphical Lasso; Inter-country contagion; Inter-sector contagion; Inter-institutional contagion; Sovereign crisis; Sparse covariance selection
    JEL: C58 E02 G32
    Date: 2020
  12. By: Pramod C. Mane; Nagarajan Krishnamurthy; Kapil Ahuja
    Abstract: This paper focuses on social cloud formation, where agents are involved in a closeness-based conditional resource sharing and build their resource sharing network themselves. The objectives of this paper are: (1) to investigate the impact of agents' decisions of link addition and deletion on their local and global resource availability, (2) to analyze spillover effects in terms of the impact of link addition between a pair of agents on others' utility, (3) to study the role of agents' closeness in determining what type of spillover effects these agents experience in the network, and (4) to model the choices of agents that suggest with whom they want to add links in the social cloud. The findings include the following. Firstly, agents' decision of link addition (deletion) increases (decreases) their local resource availability. However, these observations do not hold in the case of global resource availability. Secondly, in a connected network, agents experience either positive or negative spillover effect and there is no case with no spillover effects. Agents observe no spillover effects if and only if the network is disconnected and consists of more than two components (sub-networks). Furthermore, if there is no change in the closeness of an agent (not involved in link addition) due to a newly added link, then the agent experiences negative spillover effect. Although an increase in the closeness of agents is necessary in order to experience positive spillover effects, the condition is not sufficient. By focusing on parameters such as closeness and shortest distances, we provide conditions under which agents choose to add links so as to maximise their resource availability.
    Date: 2021–01
  13. By: Carlos León
    Abstract: Mobile wallets replicate physical wallets on a mobile device, in which users can store different payment instruments (e.g., cards, transfers) to make mobile payments. As the mobile wallet is adopted, a mobile payment scheme emerges, with its users as elements in a network of transfers. In this article, I study the mobile payment scheme of Movii— the first fintech firm in Colombia operating under a financial non-banking license for electronic deposits and payments. Based on a unique dataset of bilateral transfers between Movii’s mobile wallet users, I build, visualize and analyze Movii’s network, daily from November 18, 2017, to November 25, 2020. Besides the anticipated increase in the number of users and the value of transfers, the visual and quantitative complexity of the network of transfers increases over time. This increase in complexity is likely to be linked to the adoption of Movii’s mobile wallet, which results in users finding new ways to use mobile payments beyond person-to-person transfers, including person-to-business and business-to-business. Also, results suggest the Covid-19 pandemic accelerated the evolution of Movii’s mobile payments scheme. **** RESUMEN: Las billeteras móviles replican a las billeteras físicas en un dispositivo móvil, con las que los usuarios pueden utilizar diferentes instrumentos de pago (e.g., tarjetas, transferencias) para realizar pagos móviles. Con la adopción de la billetera móvil surge un esquema de pagos móviles, en el que sus usuarios son elementos de una red de transferencias. En este artículo se estudia el esquema de pagos móviles de Movii—la primera fintech en Colombia que opera bajo una licencia financiera (no bancaria) de depósitos y pagos electrónicos. Con base en una base de datos de transferencias bilaterales entre usuarios de la billetera móvil de Movii, se construye, visualiza y analiza la red de Movii, diaria, desde noviembre 18 de 2017 hasta noviembre 25 de 2020. Además del esperado incremento en el número de usuarios y el valor de las transferencias, se encuentra que la complejidad visual y cuantitativa de la red de transferencias se incrementa a través del tiempo. Este aumento en la complejidad tiene que ver con la adopción de la billetera móvil de Movii, lo cual resulta en que los usuarios encuentran nuevas maneras de utilizar los pagos móviles más allá de transferencias persona a persona, incluyendo pagos de persona a negocio y de negocio a negocio. Así mismo, es evidente que la pandemia por Covid-19 aceleró la evolución del esquema de pagos móviles de Movii.
    Keywords: Payments, mobile, networks, fintech, paytech, complexity, pagos, móvil, redes, fintech, paytech, complejidad
    JEL: L14 D85 E42
    Date: 2021–04
  14. By: Katya Long; Jean-Philippe Berrou (LAM - Les Afriques dans le monde - CNRS - Centre National de la Recherche Scientifique); Alain Piveteau (PRODIG - UMR 215 Prodig - UP1 - Université Paris 1 Panthéon-Sorbonne - CNRS - Centre National de la Recherche Scientifique - IRD [France-Nord] - Institut de Recherche pour le Développement - AgroParisTech, IRD - Institut de Recherche pour le Développement, PRODIG - UMR 8586 Prodig - UP1 - Université Paris 1 Panthéon-Sorbonne - IRD [France-Nord] - Institut de Recherche pour le Développement - AgroParisTech - CNRS - Centre National de la Recherche Scientifique); Thibaud Deguilhem (LADYSS - Laboratoire Dynamiques Sociales et Recomposition des Espaces - UP - Université de Paris - UPN - Université Paris Nanterre - UP8 - Université Paris 8 Vincennes-Saint-Denis - CNRS - Centre National de la Recherche Scientifique - UP1 - Université Paris 1 Panthéon-Sorbonne); Leo Delpy (GREThA - Groupe de Recherche en Economie Théorique et Appliquée - UB - Université de Bordeaux - CNRS - Centre National de la Recherche Scientifique); Claire Gondard-Delcroix (GREThA - Groupe de Recherche en Economie Théorique et Appliquée - UB - Université de Bordeaux - CNRS - Centre National de la Recherche Scientifique, UMI RESILIENCES - Unité mixte internationale Résiliences - Centre ivoirien de recherches économiques et sociales (CIRES) - Université de Cocody, IRD - Institut de Recherche pour le Développement)
    Abstract: The growing interest in social protection in Africa over the past two decades has led to a renewal of academic research and institutional literature, rang-ing from technical and evaluation approaches to political economy studies. The latter have the analyt-ical singularity of linking the outcomes of social pro-tection policies to their modalities of political inser-tion and appropriation rather than to their original conception and the manner in which they are im-plemented. As such, this report is an original contribution to the analysis of public policies in countries under foreign aid regimes. Considering the ‘political construction of public policies' as a determinant of their success, we present here an empirical analysis of the elabo-ration of Madagascar's new social protection policy. The study of the relationships between stakeholders reveals the coalitions of actors involved and their role in the ongoing changes in orientation. The empirical strategy we have chosen combines and applies the policy network and advocacy coali-tion framework (ACF) approaches by testing them with the tools of social network analysis. It is in line with the research on developed or emerging coun-tries that is rare or non-existent in low-income countries. The inter-organisational network data is drawn from a sociometric and qualitative survey carried out in 2018 and 2019 among the member organisations of the Groupe de travail sur la protec-tion sociale – GTPS (Social Protection Working Group). Under the auspices of the Ministry of Popu-lation, this group is responsible for drafting social protection policy in Madagascar. Joining the ACF and Policy Network methodological approaches, two complementary steps support our original empirical strategy. The first step deals with a structural analysis of social protection networks, using three cumulative criteria to identify coalitions of political actors. Foremost, a coalition necessary brings together structural equivalent actors within the network of collaborations (we applied one of the most relevant blockmodeling algorithm). After-ward, the coalition's subnetwork has higher within-clique density than between-clique density on col-laboration, sharing information and agreement ties. Finally, the coalition's subnetwork has higher be-tween-clique density than within-clique density on disagreement ties. The second step explores the resource circulation within the network and the cognitive consistency of each political coalition (closeness of values between actors). This then makes it possible to identify the coalition of power, with a strong capacity for mobili-sation and influence, that is at the heart of the new social protection policy. Our results show that Madagascar's approach direct-ly reflects the paradigm shift that took place in the international political arena at the turn of the 2000s. The five relational spaces under study reflect the singular way in which this has been translated in the Malagasy institutional and political context. That of a fragile, liquefied state, with a chronic inability to resolve the redistributive conflict, particularly in a phase of economic growth. Social protection policy is dominated by a ‘pro-vulnerable' or, in other words, a ‘pro-cash' coalition, which is much more decisive than the second, ‘pro-rights' coalition. Composed mainly of actors from the relief sector, the leading coalition has a view of economic security issues based on the understand-ing of individual risks and market integration. Its organization is based on the centrality of UNICEF and includes the two ministries historically in charge of social protection in the country: the Ministry of Health and the Ministry of Social Protection. The over-determining role of international donors is confirmed on analysis. In a position to control the content of social protection policy statements and of the related policy tools, negotiations with national public actors remain limited. In this configuration, where the failure of politics is reflected even in the marginalization of civil society actors, the external global offer tends to be hegemonic. However, this conclusion calls for some nuance. Although they do not occupy central positions, gov-ernment institutions (ministries and agencies) often act as brokers. They build bridges between the sep-arate worlds of social protection. Even if they do not govern social protection policy, the state and its administration disseminate its principles and ideas. This role as an interface between the central inter-national organizations and the population, which is characteristic of a country under foreign aid regime, places the government institutions in the position of a "development-broker". This encourages the re-production of resource accumulation strategies. Due to a lack of a dense internal social and political construction, social protection policy can only count on the accuracy and relevance of a comprehensive offer of protection and its financing through aid. From this point of view, the development of a new Malagasy social contract that would create solidarity is not on the agenda.
    Keywords: Social protection policy,Political Networks,Madagascar,Complete social network analysis,Advocacy coalitions,Inter-organizational relations,Public policy analysis
    Date: 2021–03
  15. By: Areejit Samal; Sunil Kumar; Yasharth Yadav; Anirban Chakraborti
    Abstract: Over the last two decades, financial systems have been studied and analysed from the perspective of complex networks, where the nodes and edges in the network represent the various financial components and the strengths of correlations between them. Here, we adopt a similar network-based approach to analyse the daily closing prices of 69 global financial market indices across 65 countries over a period of 2000-2014. We study the correlations among the indices by constructing threshold networks superimposed over minimum spanning trees at different time frames. We investigate the effect of critical events in financial markets (crashes and bubbles) on the interactions among the indices by performing both static and dynamic analyses of the correlations. We compare and contrast the structures of these networks during periods of crashes and bubbles, with respect to the normal periods in the market. In addition, we study the temporal evolution of traditional market indicators, various global network measures and the recently developed edge-based curvature measures. We show that network-centric measures can be extremely useful in monitoring the fragility in the global financial market indices.
    Date: 2021–01
  16. By: Liza Charroin; Bernard Fortin; Marie Claire Villeval
    Abstract: If individuals tend to behave like their peers, is it because of conformity, that is, the preference of people to align behavior with the behavior of their peers; homophily, that is, the tendency of people to bond with similar others; or both? We address this question in the context of an ethical dilemma. Using a peer effect model allowing for homophily, we designed a real-effort laboratory experiment in which individuals could misreport their performance to earn more. Our results reveal a preference for conformity and for homophily in the selection of peers, but only among participants who were cheating in isolation. The size of peer effects is similar when identical peers were randomly assigned and when they were selected by individuals. We thus jointly reject the presence of a self-selection bias in the peer effect estimates and of a link strength effect.
    Keywords: , Peer Effects,Homophily,Dishonesty,Self-Selection Bias,Experiment
    JEL: C92 D83 D85 D91
    Date: 2021–04–01
  17. By: Nicola Melluso; Andrea Bonaccorsi; Filippo Chiarello; Gualtiero Fantoni
    Abstract: Covid-19 has rapidly redefined the agenda of technological research and development both for academics and practitioners. If the medical scientific publication system has promptly reacted to this new situation, other domains, particularly in new technologies, struggle to map what is happening in their contexts. The pandemic has created the need for a rapid detection of technological convergence phenomena, but at the same time it has made clear that this task is impossible on the basis of traditional patent and publication indicators. This paper presents a novel methodology to perform a rapid detection of the fast technological convergence phenomenon that is occurring under the pressure of the Covid-19 pandemic. The fast detection has been performed thanks to the use of a novel source: the online blogging platform Medium. We demonstrate that the hybrid structure of this social journalism platform allows a rapid detection of innovation phenomena, unlike other traditional sources. The technological convergence phenomenon has been modelled through a network-based approach, analysing the differences of networks computed during two time periods (pre and post COVID-19). The results led us to discuss the repurposing of technologies regarding "Remote Control", "Remote Working", "Health" and "Remote Learning".
    Date: 2021–01

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