Halting SARS-CoV-2 by Targeting High-Contact Individuals

Network scientists have proposed that infectious diseases involving person-to-person transmission may be effectively halted by targeting interventions at a minority of highly connected individuals. Can this strategy be effective in combating a virus partly transmitted in close-range contact, as many believe SARS-CoV-2 to be? Effectiveness critically depends on high between-person variability in the number of close-range contacts. We analyze population survey data showing that indeed the distribution of close-range contacts across individuals is characterized by a small fraction of individuals reporting very high frequencies. Strikingly, we find that the average duration of contact is mostly invariant in the number of contacts, reinforcing the criticality of hubs. We simulate a population embedded in a network with empirically observed contact frequencies. Simulations show that targeting hubs robustly improves containment

Rational Reconstructions of Society

The dissertation contains four stand-alone studies, chapters 2 through 5. In chapter 1, I highlight commonalities among the studies. In chapter 2, I consider the principle of structural balance - "The friend of a friend is a friend, the enemy of a friend is an enemy, the friend of an enemy is an enemy, and the enemy of an enemy is a friend." I consider Harary's (1954) result that this principle can only be satisfied in a world consisting of two inimical friendship cliques. And I consider recent studies that show that when individuals in a structurally imbalanced world change ties one by one following the principle, they do not necessarily end up in a structurally balanced world. I prove that if multiple ties can be changed simultaneously, then a structurally balanced world is guaranteed. In chapter 3, I consider Burt's (1992) argument of "structural holes" that unconnected parts of a social network are niches for brokerage. I consider Burt's suggestion that those aware of brokerage benefits end up occupying structurally advantaged network positions. I show how this statement crucially depends on the unawareness of these benefits by others. If everyone strives for structural holes, no one ends up with a structural advantage. In chapter 4, I consider the extensive laboratory evidence on the relationship between the structure of small exchange networks and expected exchange rates. I consider a theory that reasonably predicts this relationship in a handful of networks. I show that if individuals add ties that increase expected earnings from exchange more than they cost and delete all other ties, then networks emerge that distribute exchange benefits equally. In chapter 5, I consider the old immigrant assimilation model of a monotonic process. I consider recent work in the direction of an alternative model. I propose an alternative model that follows up on this work and adds minimal complexity to the old model. In this model, quite assimilated migrants further assimilate, while not so assimilated migrants reverse-assimilate. Using longitudinal survey data, I show that the model is empirically competitive. In chapter 6, I propose four follow-up studies

Trust, reputation, and the value of promises in online auctions of used goods

Buyers in online markets pay higher prices to sellers who promise a highquality product in auctions of used goods, even though they cannot assess quality until after the sale. The principal argument offered in prior work is that reputation systems render sellers’ ‘cheap talk’ credible by allowing buyers to publicly rate sellers’ past honesty and sellers to build a reputation for being honest. We test this argument using both observational data from online auctions on eBay and an internet experiment. Strikingly, in both studies we find that unverifiable promises are trusted by buyers regardless of seller reputation or the presence of a reputation system, and sellers mostly refuse to take advantage. We conclude that the prevailing conception of markets in economic sociology as made possible by opportunism-curtailing institutions is “undersocialized”: Reputation systems may be used to identify more reliable providers of a product, but that they would be needed to prevent otherwise rampant deceit relies on a cynical assumption about human behavior that is empirically untenable.Published online: 15 May 202

The role of reputation systems in digital discrimination

Reputation systems are commonplace in online markets, such as on peer-to-peer sharing platforms. These systems have been argued to be a solution to (ethnic) discrimination on such platforms. This argument is based on empirical studies showing that ethnic disadvantages are smaller for users with ratings than for users without ratings. We argue that this conclusion may be premature, because minorities have a harder time accumulating ratings. The greater benefit of ratings to minorities may be offset by their troubles acquiring any, thereby diminishing the potential for reputation systems to reduce discrimination. We tested this counterargument using a unique data set that contains information on all interactions on a peer-to-peer motorcycle rental platform. We find that the reputation system does not reduce initial inequalities between otherwise comparable renters of different ethnicity. Platforms that wish to reduce discrimination should not only make their reputation system more effective, but also help users collect ratings

Prioritizing high-contact occupations raises effectiveness of vaccination campaigns

Published: 14 January 2022A twenty-year-old idea from network science is that vaccination campaigns would be more effective if high-contact individuals were preferentially targeted. Implementation is impeded by the ethical and practical problem of differentiating vaccine access based on a personal characteristic that is hard-to-measure and private. Here, we propose the use of occupational category as a proxy for connectedness in a contact network. Using survey data on occupation-specific contact frequencies, we calibrate a model of disease propagation in populations undergoing varying vaccination campaigns. We find that vaccination campaigns that prioritize high-contact occupational groups achieve similar infection levels with half the number of vaccines, while also reducing and delaying peaks. The paper thus identifies a concrete, operational strategy for dramatically improving vaccination efficiency in ongoing pandemics

Prioritizing high-contact occupations raises effectiveness of vaccination campaigns

A twenty-year-old idea from network science is that vaccination campaigns would be more effective if high-contact individuals were preferentially targeted. Implementation is impeded by the ethical and practical problem of differentiating vaccine access based on a personal characteristic that is hard-to-measure and private. Here, we propose the use of occupational category as a proxy for connectedness in a contact network. Using survey data on occupation-specific contact frequencies, we calibrate a model of disease propagation in populations undergoing varying vaccination campaigns. We find that vaccination campaigns that prioritize high-contact occupational groups achieve similar infection levels with half the number of vaccines, while also reducing and delaying peaks. The paper thus identifies a concrete, operational strategy for dramatically improving vaccination efficiency in ongoing pandemics

Limited evidence for structural balance in the family

Published online: 17 August 2023Previous studies have shown that relationship sentiments in families follow a pattern wherein either all maintain positive relationships or there are two antagonistic factions. This result is consistent with the network theory of structural balance that individuals befriend their friends’ friend and become enemies with their friends’ enemies. Fault lines in families would then endogenously emerge through the same kinds of interactional processes that organize nations into axis and allies. We argue that observed patterns may instead exogenously come about as the result of personal characteristics or homophilous partitions of family members. Disentangling these alternate theoretical possibilities requires longitudinal data. The present study tracks the sentiment dynamics of 1,710 families in a longitudinal panel study. Results show the same static patterns suggestive of balancing processes identified in earlier research, yet dynamic analysis reveals that conflict in families is not generated or resolved in accordance with balance theory