ObjectivesStudies on the management of the COVID-19 pandemic through testing have been conducted ... more ObjectivesStudies on the management of the COVID-19 pandemic through testing have been conducted in countries that have been hardest hit by this pandemic. Considering the importance of testing in containing the spread of COVID-19, it is useful to have evidence on continuing COVID-19 testing even in countries where the prevalence of COVID-19 is relatively low. We, therefore, examined the association between reported COVID-19 symptoms and testing for COVID-19 in Canada.Design and settingsWe conducted an online survey using the SurveyMonkey platform between July and October 2020 across Canada.ParticipantsA nationally representative sample size of 2790 adult individuals was used.ResultsOur findings show that respondents who reported that they and/or members of their households had COVID-19 symptoms were more likely to test for COVID-19 (adjusted OR, aOR 1.91; 95% CI 1.32 to 2.76) as compared with those who did not report COVID-19 symptoms. The likelihood of testing for COVID-19 was lowe...
A round-robin political tournament is an election format where multiple candidates contest in pai... more A round-robin political tournament is an election format where multiple candidates contest in pairs, and votes are aggregated using a general rule to form a social ranking. We formalize this tournament as a strategic form game and provide a necessary and sufficient condition under which truthful voting is a Nash equilibrium. Building on this analysis, we study the concept of effective power, defined as a voter's ability to bring about a social ranking that maximizes his preferences. We show that the classical theories of political power do not translate into effective power in general. We then provide a full characterization of the classes of political tournaments and utility metrics for which these theories capture effective power. We offer both structural and behavioral interpretations of the findings, and derive practical implications for the design of political tournaments that are compatible with truth-telling.
We consider the problem of valuing inputs in a production environment in which input supply is un... more We consider the problem of valuing inputs in a production environment in which input supply is uncertain. Inputs can be workers in a firm, risk factors for a disease, securities in a financial market, or nodes in a networked economy. Each input takes its values from a finite set, and uncertainty is modeled as a probability distribution over this set. First, we provide an axiomatic solution to our valuation problem, defining three intuitive axioms which we use to uniquely characterize a valuation scheme that we call the a priori Shapley value. Second, we solve the problem of valuing inputs a posteriori-that is, after observing output. This leads to the Bayesian Shapley value. Third, we consider the problem of rationalizing uncertainty when the inputs are rational workers supplying labor in a non-cooperative production game in which payoffs are given by the Shapley wage function. We find that probability distributions over labor supply that can be supported as mixed strategy Nash equilibria always exist. We also provide an intuitive condition under which we prove the existence of a pure strategy Nash equilibrium. We present several applications of our theory to real-life situations.
More than half of the HIV/AIDS-infected population today are women. We study a dynamic model of (... more More than half of the HIV/AIDS-infected population today are women. We study a dynamic model of (in)fidelity, which explains the HIV/AIDS gender gap by the configuration of sexual networks. Each individual desires sexual relationships with opposite sex individuals. Two Markov matching processes are defined, each corresponding to a different culture of gender relations. The first process leads to egalitarian pairwise stable networks in the long run, and HIV/AIDS is equally prevalent among men and women. The second process leads to antiegalitarian pairwise stable networks reflecting male domination, and women bear a greater burden. The results are consistent with empirical observations.
We develop a theory of how community-level ethnic heterogeneity determines the formation of sexua... more We develop a theory of how community-level ethnic heterogeneity determines the formation of sexual networks, and how this in turn affects the diffusion of HIV/AIDS. Specifically, the model assumes that agents derive utility from sexual relationships, but sexual infidelity is socially prohibited and penalized if detected. It implies a mechanism wherein ethnic heterogeneity provides incentives for optimizing agents to multiply sexual partners across ethnic groups while lowering the probability of infidelity detection, and thus positively affects the spread of HIV/AIDS. We use individual level data from six representative countries of sub-Saharan Africa to test the model. In doing so, we find a direct effect of ethnic heterogeneity on both the number of sexual partners and HIV infection. Robustness checks show that this effect is not driven by a lack of public goods in ethnically diverse communities. Interestingly, ethnic heterogeneity is shown to have no effect on anemia which is largely untreated like HIV/AIDS, but which unlike HIV/AIDS, does not involve socially prohibited human interactions. This finding supports our theory that diseases which involve socially prohibited human interactions spread through hidden and anonymous networks. Our study offers a new and fresh explanation for the high concentration of the AIDS epidemic in sub-Saharan Africa.
We study political in ‡uence in institutions where members choose from among several options thei... more We study political in ‡uence in institutions where members choose from among several options their levels of support to a collective goal, these individual choices determining the degree to which the goal is reached. In ‡uence is assessed by newly de…ned binary relations, each of which compares any two individuals on the basis of their relative performance at a corresponding level of participation. For institutions with three levels of support (e.g., voting games in which each voter may vote "yes", "abstain", or vote "no"), we obtain three in ‡uence relations, and show that the strict component of each of them may be cyclical. The cyclicity of these relations contrasts with the transitivity of the unique in ‡uence relation of binary voting games. Weak conditions of anonymity are su¢ cient for each of them to be transitive. We also obtain a necessary and su¢ cient condition for each of them to be complete. Further, we characterize institutions for which the rankings induced by these relations, and the Banzhaf-Coleman and Shapley-Shubik power indices coincide. We argue that the extension of these relations to …rms would be useful in e¢ ciently allocating workers to di¤erent units of production. Applications to various forms of political and economic organizations are provided.
We study the dynamic stability of fidelity networks, which are networks that form in a mating eco... more We study the dynamic stability of fidelity networks, which are networks that form in a mating economy of agents of two types (say men and women), where each agent desires direct links with opposite type agents, while engaging in multiple partnerships is considered an act of infidelity. Infidelity is punished more severely for women than for men. We consider two stochastic processes in which agents form and sever links over time based on the reward from doing so, but may also take non-beneficial actions with small probability. In the first process, an agent who invests more time in a relationship makes it stronger and harder to break by his/her partner; in the second, such an agent is perceived as weak. Under the first process, only egalitarian pairwise stable networks (in which all agents have the same number of partners) are visited in the long run, while under the second, only anti-egalitarian pairwise stable networks (in which all women are matched to a small number of men) are. Next, we apply these results to find that, in the long run, under the first process, HIV/AIDS is equally prevalent among men and women, while under the second, women bear a greater burden. The key message is that anti-female discrimination does not necessarily lead to (weakly) higher HIV/AIDS prevalence among women in the short run, but it does in the long run.
We study the stability and welfare properties of …delity networks. These are networks that form i... more We study the stability and welfare properties of …delity networks. These are networks that form in a mating economy with two types of agents (e.g., men and women). Each enjoys having relationships with the opposite type. However, having multiple partners is viewed as in…delity, which is punished if detected. There is female discrimination in that in…delity is punished more severely for women than for men. We obtain a complete characterization of pairwise stable networks, which is sensitive to the size of the market. In most networks, women obtain their optimal number of partners, whereas men obtain at most their optimum. Furthermore, we show that a pairwise stable network is Pareto e¢ cient if and only if it is female-optimal. Subsequently, we study how a random, unexpected information shock a¤ects women di¤erently from men. In particular, we introduce and completely characterize female-information-biased economies, which are economies in which the di¤usion of such a shock a¤ects more women than men in all pairwise stable networks. We show that female-information-biased economies are segmented (or strati…ed), with the size of each segment being determined by a correspondence. This result generalizes to a probabilistic framework. We extend the analysis to: (1) economies characterized by female-to-male subjugation, a generalization to many-to-many matching markets of the normative principle that underlies relationship formation in oneto-one and many-to-one matching markets; and (2) hierarchical mating economies, wherein each agent has a distinct social rank and higher-ranked agents are more desired as partners. We …nd that any economy of female-to-male subjugation is female-information-biased. Any hierarchical mating economy admits a unique pairwise stable network, and is female-information-biased. The model has testable implications within and beyond the …delity context. Applied to sexual markets, our analysis uncovers the social mechanism underlying the gender gap in HIV/AIDS prevalence, and demonstrates the distinct and complementary role of female discrimination, market strati…cation and social inequality in creating an HIV infection bias against women. Applied to academic markets, our …ndings highlight a factor in the persistence of inequality between academic institutions, and have implications for how new ideas a¤ect students and faculty di¤erently. Applied to the country-citizen market for highly skilled workers, the model predicts a country's brain drain as a function of its development, and derives implications for the gap between countries in the concentration of new technologies.
Media, opinion leaders, co-ethnics, family members, and friends in ‡uence our political decisions... more Media, opinion leaders, co-ethnics, family members, and friends in ‡uence our political decisions. The ways in which these in ‡uences a¤ect political cycles and (in)stability has been understudied. We propose a model of a networked political economy, where agents' choices are partly determined by the opinions of the individuals with whom they are connected in a …xed in ‡uence network. The model features two types of individuals: ideological individuals who never change their views and who seek to in ‡uence the rest of the society; and non-ideological individuals who have no political allegiance and do not in ‡uence anybody, but who can be in ‡uenced by ideological individuals with whom they are connected. We show that in ‡uence networks increase political turnout and cause non-ideological individuals who are subject to antagonistic in ‡uences to keep changing their political views. This in turn increases political cycles and instability in two ways: (1) by reducing the number of stable and popular political leaders; and (2) by worsening the tradeo¤ between political competition and the existence of a stable leader. We uncover a necessary and su¢ cient condition that characterizes all of the political technologies and network structures that guarantee political stability. This condition introduces a preference-blind stability index, which maps each pair of a constitution and an in ‡uence network into the maximum number of competing political leaders that a society can a¤ord while remaining stable regardless of the extent of preference heterogeneity in its population. Our …ndings have testable implications for di¤erent societies. They shed light on the network origins of political cycles in two-party systems. They also imply that individualist societies are more politically stable than collectivist societies and societies organized around ethnic groups or characterized by a high level of homophilous behavior and in ‡uences. For ethnic democracies, we quantify the exact tradeo¤ between political competition and stability, and show that ethnic fragmentation increases stability. The …ndings further provide a rationale for using the "divide and rule" strategy to maintain political power. Finally, we …nd that cliques and multi-layer cliques maximize the competition-stability tradeo¤, whereas star networks, lines and rings minimize it.
The right to hold dual citizenship is an important political institution that is being adopted by... more The right to hold dual citizenship is an important political institution that is being adopted by an increasing number of countries. We argue that this institution can generate important social and economic benefits beyond its political dimension. Dual citizenship recognition by a country allows members of its diaspora who are citizens of their host countries to retain several legal advantages in their homelands, including unrestricted residency and easy access to investment opportunities, and provides multiple incentives to maintain ties with family, friends and communities, therefore facilitating the development of transnational solidarity and business networks. We assemble a large panel dataset on dual citizenship, and exploit crosscountry and cross-time variation in the timing of dual citizenship recognition to estimate its economic impacts. We find that in developing countries, dual citizenship recognition increases foreign remittance inflows by US$1.19 billion, raises GDP and household consumption, favors international labor mobility, and improves child survival. Additionally, dual citizenship is more effective in improving child survival than other institutional variables such as government stability and the absence of internal and external conflicts. In developed countries, dual citizenship recognition decreases remittance inflows by US$1.44 billion, but increases gross capital formation and foreign direct investment by US$12 trillion and US$828 billion, respectively, raises household consumption, fosters trade, and provides incentives for low-and high-skilled workers to move to foreign countries. Expatriates living in dual citizenship-granting countries positively affect economic outcomes in their origin countries. We find no effect of dual citizenship recognition on public spending on health and education, which suggests that the diaspora plays little role in homeland politics.
ObjectivesStudies on the management of the COVID-19 pandemic through testing have been conducted ... more ObjectivesStudies on the management of the COVID-19 pandemic through testing have been conducted in countries that have been hardest hit by this pandemic. Considering the importance of testing in containing the spread of COVID-19, it is useful to have evidence on continuing COVID-19 testing even in countries where the prevalence of COVID-19 is relatively low. We, therefore, examined the association between reported COVID-19 symptoms and testing for COVID-19 in Canada.Design and settingsWe conducted an online survey using the SurveyMonkey platform between July and October 2020 across Canada.ParticipantsA nationally representative sample size of 2790 adult individuals was used.ResultsOur findings show that respondents who reported that they and/or members of their households had COVID-19 symptoms were more likely to test for COVID-19 (adjusted OR, aOR 1.91; 95% CI 1.32 to 2.76) as compared with those who did not report COVID-19 symptoms. The likelihood of testing for COVID-19 was lowe...
A round-robin political tournament is an election format where multiple candidates contest in pai... more A round-robin political tournament is an election format where multiple candidates contest in pairs, and votes are aggregated using a general rule to form a social ranking. We formalize this tournament as a strategic form game and provide a necessary and sufficient condition under which truthful voting is a Nash equilibrium. Building on this analysis, we study the concept of effective power, defined as a voter's ability to bring about a social ranking that maximizes his preferences. We show that the classical theories of political power do not translate into effective power in general. We then provide a full characterization of the classes of political tournaments and utility metrics for which these theories capture effective power. We offer both structural and behavioral interpretations of the findings, and derive practical implications for the design of political tournaments that are compatible with truth-telling.
We consider the problem of valuing inputs in a production environment in which input supply is un... more We consider the problem of valuing inputs in a production environment in which input supply is uncertain. Inputs can be workers in a firm, risk factors for a disease, securities in a financial market, or nodes in a networked economy. Each input takes its values from a finite set, and uncertainty is modeled as a probability distribution over this set. First, we provide an axiomatic solution to our valuation problem, defining three intuitive axioms which we use to uniquely characterize a valuation scheme that we call the a priori Shapley value. Second, we solve the problem of valuing inputs a posteriori-that is, after observing output. This leads to the Bayesian Shapley value. Third, we consider the problem of rationalizing uncertainty when the inputs are rational workers supplying labor in a non-cooperative production game in which payoffs are given by the Shapley wage function. We find that probability distributions over labor supply that can be supported as mixed strategy Nash equilibria always exist. We also provide an intuitive condition under which we prove the existence of a pure strategy Nash equilibrium. We present several applications of our theory to real-life situations.
More than half of the HIV/AIDS-infected population today are women. We study a dynamic model of (... more More than half of the HIV/AIDS-infected population today are women. We study a dynamic model of (in)fidelity, which explains the HIV/AIDS gender gap by the configuration of sexual networks. Each individual desires sexual relationships with opposite sex individuals. Two Markov matching processes are defined, each corresponding to a different culture of gender relations. The first process leads to egalitarian pairwise stable networks in the long run, and HIV/AIDS is equally prevalent among men and women. The second process leads to antiegalitarian pairwise stable networks reflecting male domination, and women bear a greater burden. The results are consistent with empirical observations.
We develop a theory of how community-level ethnic heterogeneity determines the formation of sexua... more We develop a theory of how community-level ethnic heterogeneity determines the formation of sexual networks, and how this in turn affects the diffusion of HIV/AIDS. Specifically, the model assumes that agents derive utility from sexual relationships, but sexual infidelity is socially prohibited and penalized if detected. It implies a mechanism wherein ethnic heterogeneity provides incentives for optimizing agents to multiply sexual partners across ethnic groups while lowering the probability of infidelity detection, and thus positively affects the spread of HIV/AIDS. We use individual level data from six representative countries of sub-Saharan Africa to test the model. In doing so, we find a direct effect of ethnic heterogeneity on both the number of sexual partners and HIV infection. Robustness checks show that this effect is not driven by a lack of public goods in ethnically diverse communities. Interestingly, ethnic heterogeneity is shown to have no effect on anemia which is largely untreated like HIV/AIDS, but which unlike HIV/AIDS, does not involve socially prohibited human interactions. This finding supports our theory that diseases which involve socially prohibited human interactions spread through hidden and anonymous networks. Our study offers a new and fresh explanation for the high concentration of the AIDS epidemic in sub-Saharan Africa.
We study political in ‡uence in institutions where members choose from among several options thei... more We study political in ‡uence in institutions where members choose from among several options their levels of support to a collective goal, these individual choices determining the degree to which the goal is reached. In ‡uence is assessed by newly de…ned binary relations, each of which compares any two individuals on the basis of their relative performance at a corresponding level of participation. For institutions with three levels of support (e.g., voting games in which each voter may vote "yes", "abstain", or vote "no"), we obtain three in ‡uence relations, and show that the strict component of each of them may be cyclical. The cyclicity of these relations contrasts with the transitivity of the unique in ‡uence relation of binary voting games. Weak conditions of anonymity are su¢ cient for each of them to be transitive. We also obtain a necessary and su¢ cient condition for each of them to be complete. Further, we characterize institutions for which the rankings induced by these relations, and the Banzhaf-Coleman and Shapley-Shubik power indices coincide. We argue that the extension of these relations to …rms would be useful in e¢ ciently allocating workers to di¤erent units of production. Applications to various forms of political and economic organizations are provided.
We study the dynamic stability of fidelity networks, which are networks that form in a mating eco... more We study the dynamic stability of fidelity networks, which are networks that form in a mating economy of agents of two types (say men and women), where each agent desires direct links with opposite type agents, while engaging in multiple partnerships is considered an act of infidelity. Infidelity is punished more severely for women than for men. We consider two stochastic processes in which agents form and sever links over time based on the reward from doing so, but may also take non-beneficial actions with small probability. In the first process, an agent who invests more time in a relationship makes it stronger and harder to break by his/her partner; in the second, such an agent is perceived as weak. Under the first process, only egalitarian pairwise stable networks (in which all agents have the same number of partners) are visited in the long run, while under the second, only anti-egalitarian pairwise stable networks (in which all women are matched to a small number of men) are. Next, we apply these results to find that, in the long run, under the first process, HIV/AIDS is equally prevalent among men and women, while under the second, women bear a greater burden. The key message is that anti-female discrimination does not necessarily lead to (weakly) higher HIV/AIDS prevalence among women in the short run, but it does in the long run.
We study the stability and welfare properties of …delity networks. These are networks that form i... more We study the stability and welfare properties of …delity networks. These are networks that form in a mating economy with two types of agents (e.g., men and women). Each enjoys having relationships with the opposite type. However, having multiple partners is viewed as in…delity, which is punished if detected. There is female discrimination in that in…delity is punished more severely for women than for men. We obtain a complete characterization of pairwise stable networks, which is sensitive to the size of the market. In most networks, women obtain their optimal number of partners, whereas men obtain at most their optimum. Furthermore, we show that a pairwise stable network is Pareto e¢ cient if and only if it is female-optimal. Subsequently, we study how a random, unexpected information shock a¤ects women di¤erently from men. In particular, we introduce and completely characterize female-information-biased economies, which are economies in which the di¤usion of such a shock a¤ects more women than men in all pairwise stable networks. We show that female-information-biased economies are segmented (or strati…ed), with the size of each segment being determined by a correspondence. This result generalizes to a probabilistic framework. We extend the analysis to: (1) economies characterized by female-to-male subjugation, a generalization to many-to-many matching markets of the normative principle that underlies relationship formation in oneto-one and many-to-one matching markets; and (2) hierarchical mating economies, wherein each agent has a distinct social rank and higher-ranked agents are more desired as partners. We …nd that any economy of female-to-male subjugation is female-information-biased. Any hierarchical mating economy admits a unique pairwise stable network, and is female-information-biased. The model has testable implications within and beyond the …delity context. Applied to sexual markets, our analysis uncovers the social mechanism underlying the gender gap in HIV/AIDS prevalence, and demonstrates the distinct and complementary role of female discrimination, market strati…cation and social inequality in creating an HIV infection bias against women. Applied to academic markets, our …ndings highlight a factor in the persistence of inequality between academic institutions, and have implications for how new ideas a¤ect students and faculty di¤erently. Applied to the country-citizen market for highly skilled workers, the model predicts a country's brain drain as a function of its development, and derives implications for the gap between countries in the concentration of new technologies.
Media, opinion leaders, co-ethnics, family members, and friends in ‡uence our political decisions... more Media, opinion leaders, co-ethnics, family members, and friends in ‡uence our political decisions. The ways in which these in ‡uences a¤ect political cycles and (in)stability has been understudied. We propose a model of a networked political economy, where agents' choices are partly determined by the opinions of the individuals with whom they are connected in a …xed in ‡uence network. The model features two types of individuals: ideological individuals who never change their views and who seek to in ‡uence the rest of the society; and non-ideological individuals who have no political allegiance and do not in ‡uence anybody, but who can be in ‡uenced by ideological individuals with whom they are connected. We show that in ‡uence networks increase political turnout and cause non-ideological individuals who are subject to antagonistic in ‡uences to keep changing their political views. This in turn increases political cycles and instability in two ways: (1) by reducing the number of stable and popular political leaders; and (2) by worsening the tradeo¤ between political competition and the existence of a stable leader. We uncover a necessary and su¢ cient condition that characterizes all of the political technologies and network structures that guarantee political stability. This condition introduces a preference-blind stability index, which maps each pair of a constitution and an in ‡uence network into the maximum number of competing political leaders that a society can a¤ord while remaining stable regardless of the extent of preference heterogeneity in its population. Our …ndings have testable implications for di¤erent societies. They shed light on the network origins of political cycles in two-party systems. They also imply that individualist societies are more politically stable than collectivist societies and societies organized around ethnic groups or characterized by a high level of homophilous behavior and in ‡uences. For ethnic democracies, we quantify the exact tradeo¤ between political competition and stability, and show that ethnic fragmentation increases stability. The …ndings further provide a rationale for using the "divide and rule" strategy to maintain political power. Finally, we …nd that cliques and multi-layer cliques maximize the competition-stability tradeo¤, whereas star networks, lines and rings minimize it.
The right to hold dual citizenship is an important political institution that is being adopted by... more The right to hold dual citizenship is an important political institution that is being adopted by an increasing number of countries. We argue that this institution can generate important social and economic benefits beyond its political dimension. Dual citizenship recognition by a country allows members of its diaspora who are citizens of their host countries to retain several legal advantages in their homelands, including unrestricted residency and easy access to investment opportunities, and provides multiple incentives to maintain ties with family, friends and communities, therefore facilitating the development of transnational solidarity and business networks. We assemble a large panel dataset on dual citizenship, and exploit crosscountry and cross-time variation in the timing of dual citizenship recognition to estimate its economic impacts. We find that in developing countries, dual citizenship recognition increases foreign remittance inflows by US$1.19 billion, raises GDP and household consumption, favors international labor mobility, and improves child survival. Additionally, dual citizenship is more effective in improving child survival than other institutional variables such as government stability and the absence of internal and external conflicts. In developed countries, dual citizenship recognition decreases remittance inflows by US$1.44 billion, but increases gross capital formation and foreign direct investment by US$12 trillion and US$828 billion, respectively, raises household consumption, fosters trade, and provides incentives for low-and high-skilled workers to move to foreign countries. Expatriates living in dual citizenship-granting countries positively affect economic outcomes in their origin countries. We find no effect of dual citizenship recognition on public spending on health and education, which suggests that the diaspora plays little role in homeland politics.
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Papers by Roland Pongou