Bipartite causal inference with interference, time series data, and a random network

Abstract

In bipartite causal inference with interference, interventional units might receive treatment or control, and they might affect the outcome of outcome units through their connections on a bipartite network. We study bipartite causal inference with interference based on observational data across time and a changing bipartite network. Under an exposure mapping framework, we define the immediate and carryover causal effects for each outcome unit, representing contrasts of potential outcomes under different values of the immediately preceding and past exposures, respectively, averaged over time. We establish unconfoundedness of the exposure received by outcome units based on unconfoundedness assumptions on the interventional units' treatment assignment and the random network, hence respecting the bipartite structure of the problem. Our results hold for binary, continuous, and multivariate exposure mappings. In the special case of binary exposure and carryover mappings, we propose algorithms for the immediate and carryover causal effects that combine matching and covariate balancing. We show that the bias of the resulting estimators is bounded. In our motivating study, we find some evidence that smoke from wildfires has an immediate impact on reducing transportation by bicycle in San Francisco.