Hi all,
Our next virtual meeting will be Wednesday April 1, where we will hear Soichiro
Yamauchi present research on “*Difference-in-Differences for Ordinal
Outcomes: Application to the Effect of Mass Shootings on Attitudes towards
Gun Control*”.
*Abstract*: The difference-in-differences (DID) design is widely used in
observational studies to estimate the causal effect of a treatment when
repeated observations over time are available. Yet, almost all existing
methods assume linearity in the potential outcome (parallel trends
assumption) and target the additive effect. In social science research,
however, many outcomes of interest are measured on an ordinal scale. This
makes the linearity assumption inappropriate because the difference between
two ordinal potential outcomes is not well defined. In this paper, I
propose a method to draw causal inferences for ordinal outcomes under the
DID design. Unlike existing methods, the proposed method utilizes the
latent variable framework to handle the non-numeric nature of the outcome,
enabling identification and estimation of causal effects based on the
assumption on the quantile of the latent continuous variable. The paper
also proposes an equivalence-based test to assess the plausibility of the
key identification assumption when additional pre-treatment periods are
available. The proposed method is applied to a study estimating the causal
effect of mass shootings on the public’s support for gun control. I find
that the effect is concentrated on left-leaning respondents who experienced
the shooting for the first time in more than a decade. A copy of the paper
can be found here <https://soichiroy.github.io/files/papers/ordinal_did.pdf>
.
*Zoom link*:
https://harvard.zoom.us/j/987462892
*When*: Wednesday, April 1 at 12noon - 1:30pm.
Best,
Georgie