Airborne disease transmission during indoor gatherings over multiple time scales: Modeling framework and policy implications.

Indoor superspreading events are significant drivers of transmission of respiratory diseases. In this work, we study the dynamics of airborne transmission in consecutive meetings of individuals in enclosed spaces. In contrast to the usual pairwise-interaction models of infection where effective contacts transmit the disease, we focus on group interactions where individuals with distinct health states meet simultaneously. Specifically, the disease is transmitted by infected individuals exhaling droplets (contributing to the viral load in the closed space) and susceptible ones inhaling the contaminated air. We propose a modeling framework that couples the fast dynamics of the viral load attained over meetings in enclosed spaces and the slow dynamics of disease progression at the population level. Our modeling framework incorporates the multiple time scales involved in different setups in which indoor events may happen, from single-time events to events hosting multiple meetings per day, over many days. We present theoretical and numerical results of trade-offs between the room characteristics (ventilation system efficiency and air mass) and the group's behavioral and composition characteristics (group size, mask compliance, testing, meeting time, and break times), that inform indoor policies to achieve disease control in closed environments through different pathways. Our results emphasize the impact of break times, mask-wearing, and testing on facilitating the conditions to achieve disease control. We study scenarios of different break times, mask compliance, and testing. We also derive policy guidelines to contain the infection rate under a certain threshold.

Localized prosocial preferences, public goods, and common-pool resources.

The presence of prosocial preferences is thought to reduce significantly the difficulty of solving societal collective action problems such as providing public goods (or reducing public bads). However, prosociality is often limited to members of an in-group. We present a general theoretical model where society is split into subgroups and people care more about the welfare of others in their own subgroup than they do about those in out-groups. Individual contributions to the public good spill over and benefit members in each group to different degrees. We then consider special cases of our general model under which we can examine the consequences of localized prosociality for the economic outcomes of society as a whole. We ask to what extent prosociality closes the welfare gap between the Nash equilibrium without prosociality and the social optimum. The answer depends on whether private and public inputs are good or poor substitutes in producing final output. Critically, the degree to which this welfare gap closes is a concave function of the level of prosociality in the case of poor substitutes, so even low levels of prosociality can lead to social welfare near the social optimum.

Political polarization.

Failures of government policies often provoke opposite reactions from citizens; some call for a reversal of the policy, whereas others favor its continuation in stronger form. We offer an explanation of such polarization, based on a natural bimodality of preferences in political and economic contexts and consistent with Bayesian rationality.