A Simple Approach to Staggered Difference-in-Differences in the Presence of Spillovers

Authors: Mario Fiorini, Wooyong Lee, Gregor Pfeifer

Date of publication: January 2024

Working paper number: 02

Abstract:

We establish identifying assumptions and estimation procedures for the ATT in a Difference-in-Differences setting with staggered treatment adoption in the presence of spillovers. We show that the fully interacted TWFE regression approach of Wooldridge [2022] can be extended to our proposition. We broaden our framework to the non-linear case of count data and revisit a corresponding application from the crime literature. Monte Carlo simulations show that our estimator performs competitively.

Keywords: Difference-in-Differences, staggered treatment adoption, spillovers, (non-)linear models

Acknowledgement of Country

UTS acknowledges the Gadigal people of the Eora Nation, the Boorooberongal people of the Dharug Nation, the Bidiagal people and the Gamaygal people, upon whose ancestral lands our university stands. We would also like to pay respect to the Elders both past and present, acknowledging them as the traditional custodians of knowledge for these lands.