Questions tagged [generalized-did]

This is the generalized Difference-in-Differences

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Fixed effects difference in differences issue

I am currently conducting a difference in difference (DID) analysis and fail to understand the benefits of fixed effects models in such cases. I ran a regular DID model with three regular independent ...
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Event study renders treatment effect significant

Currently, I am working with crime panel data (county-day level over several years) to investigate the effect of police presence on crime. I use an "exogenous" increase in police presence ...
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How to make the case for a parallel trends assumption in a within-person DiD with 1 pre-treatment time point 1 post-treatment time point?

Study design: Within a two-year period (2021-2022), both the people in the treatment group and the people in the control group did not receive the treatment of interest at time point #1, and only the ...
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Adding district year fixed effects in a two year panel employing individual fixed effects

The data I have is longitudinal with two survey rounds. So I have a two-year panel. In the empirical set up I have employed individual fixed effects. Is it wrong to employ district-by-survey fixed ...
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Stacked difference in difference with treated units appearing in different cohorts

I am estimating a stacked difference in difference following slide 35 here: I will call a subexperiment as a "cohort". Here, $\theta_{sd}$ are unit $\times$ cohort fixed effects and $\...
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How to generate placebo test for random false treatment?

I would like to do a placebo test to ensure the result of my main staggered DID results. I have a country-level mandate that goes into effect in different years during my sample period, and in some ...
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DiD control treatment group choice

I need to evaluate the impact of the Labour-Intensive Public Works programme on social cohesion using DiD. I chose a set of control variables and an outcome variable. The thing is to choose the right ...
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Any way to test if the association between X and Y could be causal, reverse-causal or non-causal (just correlation)?

I'm doing a regression between Institutional Investment and Total Debt for 500 companies over 2000-2022. Basically, it's panel data. I get the results of the regression and I see that the two are ...
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Figuring out if my problem is about a difference-in-differences with a continuous treatment

I am interested to find the causal effects of a state level policy on some outcome of interest. The policy affects some states each year but not other states. The states that are affected can vary ...
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DID with Panel data (FE) - insignificant results

I run a DID with Panel data (FE) in Stata. I have two groups, Treatment Group (N=75); Control group (N=54). And have a time series of 6, 3 pre treatment and 3 post treatment. I am getting ...
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Does it satisfy Parallel trend assumption if coef before the shock is non-zero yet constant over time?

A shock happened in early 2003. I want to estimate how the shock changed the impact of X. However, X existed all the time even before 2003. That's a difference from typical DID setting where X happens ...
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DiD with differing durations of pre-start and post-start periods by individual

Referencing this Q/A, Andy offers two models that return the DiD lift estimate. Eq1: 𝜌=(𝐸[𝑌𝑖𝑠𝑡|𝑠=𝐴,𝑡=2]−𝐸[𝑌𝑖𝑠𝑡|𝑠=𝐴,𝑡=1])−(𝐸[𝑌𝑖𝑠𝑡|𝑠=𝐵,𝑡=2]−𝐸[𝑌𝑖𝑠𝑡|𝑠=𝐵,𝑡=1]) Eq2: 𝑌𝑖𝑡=�...
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Generalized Difference in Differences model: time*group interaction contradicts lift

I've constructed a Bayesian Generalized Difference in Differences model. I model an intercept as well as three coefficients; one for treatment_group assignment, one for post-start period, and one for ...
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How to choose features to condition on in DiD causal model?

I’m looking at CausalPy documentation and the algorithm of interest ir Difference in Differences. I see that they build two different models. In general, how should one select the features and/or ...
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Dynamic effects of non-staggered difference in difference

Say I have the following treatment: \begin{array}{cccccccccc} \hline unit & year & treatment & d^{-3} & d^{-2} & d^{-1} & d^{0} & d^{+1} & d^{+2} & d^{+3} \\ \...
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Matching, event study and cohort data

I have merged data to create an event study for the treated population. This treatment happens in 4 batches for some university students in certain cohorts (when they turn 19 in 2005 and are at ...
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Staggered difference-in-difference with continuous treatment

I want to estimate a staggered difference-in-difference (DD) with continuous treatment. The data looks something like this: $$ \begin{array}{ccc} Individual & year & CT_{i,t} \\ \hline 1 &...
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How to improve difference-in-differences graph?

I want to visualise what basically is a difference in difference graph but in a better way. My first idea was two split violin plots and it looks good but is too complex for the reader. Any ideas on ...
magisterludi's user avatar
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What does an xtreg equation look like?

I ran some FE regressions in Stata using xtreg. One “normal” fixed effects model and a second generalized difference-in-differences model. Now, I am wondering how ...
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Difference in Difference estimator using PSM and time varying covariates

Which is the most appropriate DID estimator when we are studying the impact of certain policies on firms across different countries where some firms adopted the policy in every country at diiferent ...
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Multiple treatment timings and intensities Difference-in-Difference model

I have a question regarding the Difference-in-Difference model. My data consists of three groups: control, intensity 1 and intensity 2. Both treatment groups have two moments of treatment, essentially ...
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Generalized difference-in-differences without unit specific effects

Can I get some help in answering the following task? I figured it is generalized difference-in-differences (DiD) (the task is called "RCT and DiD"), but I don't know how to circumvent the ...
Kristian Nygård Solvik's user avatar
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Purpose of differences in differences with multiple time dummies

I understand that the standard difference in differences with 2 groups, 2 time periods appears as follows \begin{align*} y = \beta_0 + \beta_1Tr + \beta_2Post + \beta_3 Tr \times Post + u \end{align*} ...
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Perfect Multicollinearity in Difference in Differences

I have a set of cities for which approximately half received an intervention and half did not. The intervention was a drug treatment program. All the cities that received the intervention received it ...
Pat Berrigan's user avatar
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What might be the identification challenges with a generalized DiD model where the treatment variable experiences reversals (switches on/off)?

I have a setting where my treatment variable experiences reversals across the panel units in a staggered adoption setting. To estimate the average treatment effects on the treated in a setting that ...
Ahmed Chaudhry's user avatar
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When we can ignore clustering?

I think it is a practical headache rising when doing empirical research. I am examining the impact of anticollusion laws on firms' asset growth as Dasgupsta, 2019 uses the genralized Difference-in-...
Phil Nguyen's user avatar
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How to explain the coefficient plotting as pre-trend stability testing for generalized Difference-in-Differences?

Proving the pre-trend parallel is hard in generalized DiD. From this post, Thomas Bilach suggests me a very excellent way to do so which is called "coefficient plotting" In short, it can be ...
Phil Nguyen's user avatar
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Is there any common way to do pre-trend analysis for generalized Difference in Difference?

The generalized difference-in-differences (DiD) estimator is DiD with multiple time periods and multiple groups. A very common example is when the impact of laws on firms happens at different times, ...
Phil Nguyen's user avatar
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How to plot the graph or perform a formal test of parallel trends for generalized DiD?

A. Background: Dasgupta, 2019, p. 2596-2597 create a baseline as below to study the impact of staggered design difference-in-differences (DiD): The baseline identification: $Y_{it}$ = $\alpha$ + $\...
Phil Nguyen's user avatar
3 votes
1 answer
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Fixed effects in differences-in-differences

In a differences-in-differences it is quite typical to have $y_{ist} = \lambda_t + \alpha_s + \beta_1D_{s,t} + \epsilon_{ist}$, where $\lambda_t$ is a time fixed effect and $\alpha_s$ is a group ...
Daniel Pinto's user avatar