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Questions tagged [difference-in-difference]

Often abbreviated DID or DD, this is a technique for inferring causality from observational data. It involves comparing measurements before and after a treatment occurs (hence, the growth rate) in both a group that received the treatment, and an otherwise comparable group that did not.

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Difference in Difference with continuous treatment variable

I want to see the effect of conflict which causes fatalities in a region on the performance of financial institutions. I have data from 2015 to 2022 for 8 institutions operating in 8 counties. The ...
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Diff-in-Diff with multiple time periods

this is my first post here and I'm very new, I hope this is somehow clear. For context: For my master thesis, I want to estimate the effect that replications have on the citations of a paper. For this,...
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How should I test for parallel trend assumption in a repeated cross-sectional data?

I have a repeated cross-sectional dataset on time-use which I am using to estimate the impact of a certain shock. My outcome of interest is time spent by certain individual on particular activity. ...
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Negative log-likelihood, high BIC, high R-squared, low error, using a difference-in-differences (DiD) methodology [closed]

I am trying to see the impact of Brexit on UK imports. My dependent variable are EU exports to the rest of world. I have monthly data from 2013 to 2023, also data is in billions of GBP. When I do ...
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Diff-in-diff with an unbalanced panel

Say I want to study the effect of some intervention using a diff-in-diff setup. I have a panel of units observed during some period. I can identify treated/non-treated groups and pre/post periods (...
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Using Controls that are time-invariant with the difference-in-differences estimators

I ran an experiment in which there was 2 groups of participants performing the exact same task during a first period. In the second period, the two groups had to perform the same task a second time. ...
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Test of difference of Coefficients of a same regression [duplicate]

Sir I have run a regression, where I estimated effect of two independent variables A and B on an outcome variable C. How can I compare the regression coefficients of A and B to estimate whether the ...
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Should I control for unit-specific linear time trends in difference-in-differences

I have a staggered difference-in-differences setup and have been wondering whether I should be including group/unit-specific linear time trends in my model. It seems to be a common feature in the ...
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Difference-in-differences or difference-in-difference-in-differences using a Randomized control trial

For an academic project I have been given a data set on a Randomized Control Trial. I need to use this dataset to derive the treatment effects of a ‘Crop harvestor’ technology. Data - The data is on ...
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Best Practices for Applying Difference-in-Differences in Panel Data Analysis: Addressing Imbalance and Identifying Suitable Matching Techniques

I am conducting a study on the impact of the African Growth and Opportunity Act (AGOA) on apparel exports from Sub-Saharan Africa using panel data, including 20 treatment countries under the Special ...
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Difference between reghdfe and fixest for a multiple FE regression?

I am estimating the following equation using fixest: $$ Y_{i,f,s,t} = \beta_1 treat_i + \beta_2 post_t + \beta_3 treat_i*post_t + \alpha_i + \alpha_{s,t} + \alpha_{f,t} + \epsilon_{i,f,s,t} $$ where ...
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Difference in differences event study to support parallel trends

I did an analysis using a Difference-in-Differences setup with a staggered treatment design and conducted an event study to verify the parallel trends assumption. The attached figure for one of the ...
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What estimator and R package can be used for staggered difference-in-difference with (non-panel) cross-sectional data, controls and interactions

I am trying to run a difference-in-difference analysis in R. My data is non-panel, so I am reliant on a TWFE model where I have groups of individuals who are ...
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Can I test if a difference for a single subject is large enough to consider that subject an outlier from a population of subjects?

I have measurements of vegetation bed size for four beds before and after an event. Three of the beds are unaffected by the event and all changed in size. One of the beds may have been affected by the ...
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Event study: Group periods at margins

For an event study (staggered Diff-in-Diff with different treatment periods) I would like to group the periods at the edges so that we get the coefficients for <=x / >=x , such as: For starters,...
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How to know whether I should use DiD or Spatial RDD?

I'm quite new in econometrics. I want to study a nationwide policy change at the city-level. In year T-1, cities are divided in three zones (green, orange, red) depending on their tension on the ...
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Granular difference-in-differences with non-repeating unit of observation

I want to analyze changes in characteristics of job postings around an (exogenous) event. However, rather than conducting the analysis at the job poster level (e.g., a company or geographic area), my ...
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2 votes
1 answer
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Why the confusion in Difference-in-Differences with pre-intervention/post-intervention periods and treated/control units?

In Difference-in-Differences, it typically has a pre-intervention and a post-intervention periods. This is coupled with treated and control units. From what I understand, since the comparison for the ...
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Applying a difference-in-differences design where the comparison group is treated in all time periods

Is it okay to apply a generalized difference-in-differences (diff-in-diff) framework when the reference group has been treated from the beginning? In my scenario, the study spans 4 time periods: $t = {...
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CUPED vs. Diff-in-Diff

I've recently come across a method known as "Controlled-experiment Using Pre-Existing Data" (CUPED), which is a regression adjustments technique to create unbiased estimators in experiments. ...
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Statistical test of increase between groups in two time periods (categorial data)

I would like to check if percentage change between the groups and time for binominal variable is significantly different. What test to use? In Group A (n = 1000) in t0 we had a 10% share that ...
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Event study regression specification: interacting covariates with leads and lags

I want to create an event study regression specification for the following: $$ \ln(y_{ijt}) = \gamma \ln (x_{jt}) + \tau \ln(p_{t}) + \lambda \ln(x_{jt}) * \ln(\mbox{p}_{t}) + \epsilon_{ijt}. $$ I am ...
specfunctor's user avatar
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How to understand why the two period Differences-in-Differences estimator is the ATT estmator?

I read in a paper here that in a two time period differences-in-differences scenario where it claims the DiD estimator is the ATT (Average Treatment on Treated). I am trying to understand why that is. ...
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Difference in difference regression with multiple treatments & a binary outcome

I’m trying to assess the impact on a “Business A” when its customers interact with a competitor business for the first time. I’m using difference in difference regression to gauge this, and the ...
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Diff-in-diff with balanced panel: adding fixed effects does not change coefficients?

I'm trying to run a differences-in-differences model in Stata. My dependent variable is order volumes, each observation is 1 store, and my panel is strongly balanced (20 quarters for each store, 6K ...
Mike's user avatar
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2 votes
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Is a regression discontinuity with two-way fixed effects a type of Diff-in-Diff?

I recently read a paper which used a regression discontinuity design (RDD) to study the effects of a law. The key variable was = 1 for all counties following the introduction of the ban. The model ...
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Difference-in-difference for multiple eco-friendly events

I am conducting one research evaluating the influence of eco-friendly events in cities (e.g., bike only for some streets on Sunday) on people's exercising habits (distance to walk in the cities). In ...
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Difference-in-Differences with Multiple Time Periods: 'Always treated' group?

The title of the post refers to this paper by Callaway & Sant'Anna: https://www.sciencedirect.com/science/article/pii/S0304407620303948?via%3Dihub Let us assume that I have data on incidence ratio ...
agallego's user avatar
3 votes
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Best Practices for Difference-in-Difference Analysis of Quasi-Experimental Repeated Cross-Sectional (Cat.) Data Different Samples per Neighborhood

I'm working with repeated cross-sectional data where each measure comes from a different sample of respondents per neighborhood. My study aims to evaluate the impact of varying police patrol levels (...
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Difference in difference, same introduction time but different duration

I am looking at a case where you take a 2-year degree. I do not have panel data, each person is observed once. I have cohorts for the years 2013-2019. I have two groups. A control group and a ...
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DiD vs Repeated meausres ANOVA vs ANCOVA

I am learning statistical analyses for experimental and quasi-experimental studies. From my class and by searching answers here and asking ChatGPT, I have some preliminary understandings of Difference-...
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Apply Difference-in-Differences to Pre Cost Comparison

Context: There are two groups of users ('Control' and Test') that are randomly assigned at the beginning. (Let's assume they finished allocation right before week 0 and not accepting new users and ...
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Exogenous but non-random event for DiD

I have a quick question regarding whether the following event might pose any issues for my study. I am interested in exploring perceptions of climate change. In the early 1970s, former dictator Park ...
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Parallel Trend and DID Estimation

I am trying to estimate the effect of climate shock on hours spent in paid labor by women. The key independent variables are time dummy (that takes 1 if shock happened, 0 otherwise; there are two pre-...
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How to cope with pre-trend violations in a stacked DiD?

I want to analyze several events using a difference-in-difference approach. Since the events occurred at different times, a staggered or stacked DiD approach would be suitable. In my case, I have many ...
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Choosing Regression Discontinuity or Difference in Difference?

I am interested in investigating the impact of a policy implemented in 2020 aimed at fostering sustained engagement in music-related activities. This policy involves providing a Conditional Cash ...
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Controlling for Time-Varying Work Factors in Dynamic DID Analysis: Handling Staggered Adoption of Child Care Leave

I'm working on a dynamic Difference-in-Differences (DID) analysis to assess the impact of child care leave on individuals' wages over their working life. My database includes information on the date ...
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Difference-in-difference age groups

I would appreciate your help with a question I have. I'm creating a Difference-in-Difference study to examine how a conditional cash transfer to individuals 18 years of age to be spent in sport ...
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Using diff-in-diff and fixed effects in Stata

I am doing research using Stata on state-level contraception policy effects on male labour outcomes (e.g. wages). I am utilizing the laws between 1960 and 1976 when Roe vs. Wade was not ruling and the ...
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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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I have a significant change in my outcome with the opposite sign in the lead period. Is this an issue?

Suppose I have a negative significant effect of a variable x on y. Also negative significant effect of the lag ie variable L1.x on y . But I get a positive sign significant effect on y in the future ...
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Using instrumental variable in a difference-in-differences setup using feols

I have the following regression model: $$y_{ist} = \beta_0 + \beta_1 Post_{ist} + \beta2 Post_{ist} \times Distance_{i} + \theta_i + \alpha_t + \gamma_{st} + \epsilon_{ist} $$ Where, $y_{ist}$ is the ...
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What happens to the parallel trends assumption when we estimate unit fixed effects at the micro level in TWFE?

I am a bit confused about the recent difference-in-differences/ two-way fixed effects literature. For example, in this paper the authors analyse a policy effect that happened at a state level on ...
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1 vote
1 answer
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What is the difference between pointwise confidence interval and uniform confidence interval in econometrics?

I'm reading Callaway, Bacon, Sant'Anna (2021) paper on continuous treatment. In section 6 they show their result of applying their proposed method to Acemoglu and Finkelstein (2008) medicare example. ...
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5 votes
1 answer
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Performing a Difference-in-Difference Analysis where the Control Group is Already Treated

I'm involved in a project where the outcome is the proportion of cancer patients who have received surgery. The treatment event is a state-level policy change that mandated moving all these cancer ...
user8408275's user avatar
1 vote
1 answer
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Difference-in-differences when treatment status is revoked

I am trying to analyze the effect of receiving "elite" status on a university's number of international first-year students. I have a perfectly balanced panel of 17 universities over an 18-...
Stephanie's user avatar
4 votes
1 answer
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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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Staggered DiD: Single Treatment

Consider a study involving subjects from 30 cohorts. The key event is a law passed by the Federal Government in 2017, which banned the use of certain vaping products. Among the 30 cohorts, individuals ...
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If I use repeated cross-sectional data in a DiD setting, what are the conditions required for my study to be causal?

I am new to statistics and I want to explore the impact of a specific policy reform. The treatment year is 2014, and I have 7 waves of post-treatment surveys along with 9 waves of pre-treatment ...
Val's user avatar
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Robust Difference-in-Differences: What is the propensity score doing?

Callaway and Sant'Anna (2022) describe a doubly robust difference-in-differences (DiD) method that is attractive in staggered DiD (multi-group treatment times) for several reasons. It can prevent &...
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