International Society of Dynamic Games

Dynamic Games and Applications Seminar

On the design of public debate in social network

April 11, 2024 11:00 AM — 12:00 PM (Montreal time)

Zoom webinar link

We propose a model of the joint evolution of opinions and social relationships in a setting where social influence decays over time. The dynamics are based on bounded confidence: social connections between individuals with distant opinions are severed while new connections are formed between individuals with similar opinions. Our model naturally gives raise to strong diversity, i.e., the persistence of heterogeneous opinions in connected societies, a phenomenon that most existing models fail to capture. The intensity of social interactions is the key parameter that governs the dynamics. First, it determines the asymptotic distribution of opinions. In particular, increasing the intensity of social interactions brings society closer to consensus. Second, it determines the risk of polarization, which is shown to increase with the intensity of social interactions. Our results allow to frame the problem of the design of public debates in a formal setting. We hence characterize the optimal strategy for a social planner who controls the intensity of the public debate and thus faces a trade-off between the pursuit of social consensus and the risk of polarization. We also consider applications to political campaigning and show that both minority and majority candidates can have incentives to lead society towards polarization.

(with A. Mandel and A. Rusinowska).

Dynamic Games and Applications Seminar

Statistical discrimination without knowing statistics: blame social interactions?

April 25, 2024 11:00 AM — 12:00 PM (Montreal time)

Zoom webinar link

We consider a model where decision makers repeatedly receive candidates and assign to them a binary decision that we can interpret as hire/not hire. The decision makers base their decision on the characteristics of the candidate but they are also sensitive to the social influence exerted by the observed past choices of their peers. We characterize the long run frequency of decisions in the model, and show in particular that for candidates belonging to a group with ”un- favorable” characteristics, the dynamics increase the rejection rate compared to a scenario with independent decisions, suggesting that social influence between decision makers can generate effects very similar to those that result from statistical discrimination. We then analyze how the existence and magnitude of a reinforcement in rejection rates depend on different properties of the distribution of characteristics in the candidate population.

Dynamic Games and Applications Seminar

The social value of information in times of epidemic

April 4, 2024 11:00 AM — 12:00 PM (Montreal time)

Zoom webinar link

We analyze an epidemiological model in which individuals trade the costs and benefits of self-isolation while being uncertain about both their type and the dynamics of the epidemic. We characterize the unique symmetric equilibrium and show that uncertainty can be the cause of an additional wave of infections. We calibrate our model to the COVID-19 pandemic and simulate the dynamics of the epidemic under various scenarios to illustrate the impact of uncertainty on self-isolation behaviors. We show that uncertainty about the epidemic dynamics may be welfare improving, both in terms of fraction of deaths and average payoffs. (with Dominique Baril-Tremblay and Lucie Ménager)