by Dr. Panos Toulis, (University of Chicago, Booth School of Business)

Abstract: This talk presents an ongoing large field experiment in a country of South America that randomizes tax audit notices (treatment) to firms connected through a large network of VAT transactions. While the ultimate goal is to optimize tax audit policy, the short-term goal is to estimate causal effects of tax audit notices on firm behavior. Of particular interest is to understand spillovers, that is, the response of firms that are not treated but are connected to other firms that are treated. First, I will discuss why current popular approaches to experimenting on networks are limited by the reality of inter-firm networks, such as their size, high interconnectivity and heavy-tailed degree distributions. I will then describe an approach to experimentation that leverages subtle sub-structures in the network. This approach is specifically designed to allow the application of Fisherian-style permutation tests of causal effects. These testing procedures are computationally efficient and finite-sample valid, qualities that are important for testing in a robust way the parameters of structural economic models.