Complementarity, Congestion and Information Design in Epidemics with Strategic Social Behaviour

This paper studies how private information about health states affects social distancing behaviour in epidemics. We propose a social-interaction game where agents are rational and demographically heterogeneous, and the risk of death post-infection depends on demography. Self-tests and public screening campaigns jointly determine the available information. We find that private information determines how the spatial characteristics of the social environment affect agents’ strategic interplay: if private information is not available, social distancing decisions are strategic substitutes in any environment; if private information is available, complementarity arises in congestionable environments, and substitutability prevails otherwise. Policy implications ensue: if self-tests that detect illness are freely available, mass screening campaigns with tests that detect recoveries are beneficial in congestionable environments, but increase the death toll in the absence of congestion.