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.

Filter by
Sorted by
Tagged with
1
vote
0answers
11 views

Panel data 'binary' treatment with multiple 'odd' start and end times

I am investigating the impact of a county-level policy on crime outcomes. I am using a two-way fixed effects estimator. My exposure (i.e., treatment) is a static binary variable. The binary treatment ...
1
vote
1answer
35 views

treatment effect on unbalanced panel data

I have an unbalanced dataset that contains movie sales data along with some of the characteristics of the movies for several years. One treatment (event) happened in the society in a specific year in ...
0
votes
1answer
45 views

Should the treatment effect coefficient in a difference-in-difference model be consistent with graph trend?

I am running a difference-in-difference regression and the coefficient of the interaction term (treat*post) is negative, so I concluded that the effect of the treatment was negative on the outcome ...
0
votes
0answers
31 views

Calculating standard errors by hand for difference in differences

If I am running a difference in difference as the following: $y_{i,t}=\beta Treat_i x Post_t + Post_t +Treat_i + \epsilon_{i,t}$ Where i can index say, state, and t time. If I wanted to calculate the ...
0
votes
0answers
24 views

Cluster issues for treatment effects analysis

I'm doing a Difference in Differences exercises on 32 regions within a country to test for the effect of a policy intervention. However, only 1 of those regions has been subject to the intervention; ...
0
votes
0answers
29 views

Why diff-in-diff over regression with control variable for measuring treatment intervention in time series?

Let's suppose we have a time series data set, with an intervention period for the treatment where the mean of the independent variable increases by 10. The goal is to measure the effect of the ...
0
votes
0answers
10 views

Log-level or growth as dependent variable in difference-in-difference model

I want to analyse the effect of a shock in pollution on rainfall and run into a little discussion with my coauthor. The shock does not affect all regions, but occurs at the same time. We decided to ...
2
votes
0answers
19 views

Help with Difference in Difference Variance Estimator (SEO Experimentation)

I found the following article https://medium.com/airbnb-engineering/experimentation-measurement-for-search-engine-optimization-b64136629760 regarding SEO frameworks. It seems to solve the issues of ...
1
vote
1answer
45 views

If fixed effects and robust standard errors both necessary, do they have to be at the same level, and why?

I am working on an empirical paper using repeated cross-sectional data, and a reviewer has asked that we cluster our standard errors at the same level as our geographic fixed effects. Given the ...
0
votes
0answers
14 views

What would be best, using turnout levels or rates as the dependent variables?

I'm looking at the effect of a specific registration requirement on turnout and have been trying to decide what form the dependent variable should take. My two main options are turnout levels (i.e. ...
0
votes
1answer
20 views

Event Study regression standard errors

When running an 'event study' diff in diff, i.e. : $y_{i,t} = \sum_{k\neq-1}\beta_k *1\{t=k\} + \lambda_t + \mu_i +error$ where i is a group level(i.e. individual, county etc). and t is time, $\...
0
votes
0answers
14 views

Why is the sign of coefficient of the fitted logistic regression and fitted linear regression different?

I was using logistic regression to fit the diff-in-diff data (the original y is a dummy variable). However, the sign of the fitted function is contrary to what I expected. Based on the mean of y ...
2
votes
0answers
47 views

Difference-in-differences estimator for time-invariant subgroups

I have a standard difference in differences (DiD) model $$ Y_{i,t} = \beta_0 + \beta_1 treat_i + \beta_2 time_t + \beta_3 (treat_i \cdot time_t) + \varepsilon_{i,t} $$ where $treat_i$ is a dummy ...
2
votes
1answer
43 views

Aggregate-level difference-in-difference analysis

Thank you in advance. I am new to difference-in-difference (DID) analysis. I want to conduct a research project examining an educational policy shock to local school districts. I have aggregated ...
1
vote
2answers
70 views

Difference in Differences - why do we use the terms 'control group' and 'treatment group'?

When doing Difference in Differences, we basically pretend to know the average treated outcome $\frac{\sum_{i=1}^n Y_i(1)}{n}$ and the average no-treatment outcome $\frac{\sum_{i=1}^n Y_i(0)}{n}$ of ...
1
vote
1answer
73 views

Event Study with two treatments

Lets say I wanted to include two different treatments in a diff in diff at the same time, so I could have: $y_{i,t} = \lambda_i +\tau_t + Treat1_i*post_t+Treat2_i*post_t + \eta_{i,t}$, where $\...
0
votes
1answer
23 views

How to deal with the standard error of fixed-effect in lmer using r?

I have a time series data across different locations with pre-post indicator. Also there are some locations belong to one intervention group and some other belong to a different intervention group. I ...
0
votes
0answers
27 views

Event study with time-varrying treatment intensities

I did a diff in diff to determine the effect of a policy that was implemented nationally time t=0, ( i.e. treatment occured nationally at time t=0). I use some pre-existing characteristics in various ...
3
votes
1answer
79 views

Is a DID model appropriate?

Suppose I have 3 groups (US states). One group has always had a "treatment" throughout the time period (always had a specific legal prohibition). One group never had the "treatment"...
4
votes
1answer
59 views

Interpreting difference in difference event study regressions

Lets say I have a model: $$ y_{i,t}= \sum_{k \neq -1} \beta_k \times treat_i \times \mathbf{1}_{K = k} + \lambda_t + \mu_i + e_{i,t}, $$ where $k$ indicates event time, and treatment takes place at ...
1
vote
0answers
31 views

Difference in difference with interaction (Part 2)

I'm conducting a difference-in-difference analysis, where I believe that my treatment effect is driven by a specific set of treatments (e.g., treated by a higher qualified teacher, compared to treated ...
0
votes
1answer
72 views

Diff-in-Diff time varying treatment

I would like to estimate a Difference in Difference specification where the treatment (i.e., the policy change P) is off then on and then off again: ...
0
votes
1answer
73 views

Why are my coefficients too large when control variables are not added?

I am doing a difference in differences analysis with staggered treatment time. Since the treatment time is different among subjects, I made my matrices look something like this from this post (Dynamic ...
0
votes
1answer
52 views

Household fixed effects with cross-sectional data

I'm trying to estimate a difference-in-difference model with pooled cross-sectional data. In order to test the parallel trends assumption, I'm following Common trend assumption by running Y_it = ...
1
vote
0answers
20 views

Difference-in-difference: standard errors in nonparametric estimation and linear regression

It is well known that we can use a linear regression model to calculate the DiD estimate. I followed this website and created a simulation dataset. ...
0
votes
1answer
34 views

Identical Coefficients for DiD with and without FE

I have a data set which includes monthly luminosity data for 3000 municipalities in Mexico. I also have one observation of several census covariates for each municipality. My data looks like this <...
2
votes
0answers
25 views

Difference-in-Differences time-variant control variable

I conduct a staggered difference-in-differences analysis across multiple groups i and multiple time periods t. Therefore, I fitted a fixed-effects model using the following equation: $$ Y_{it}=\beta_{...
1
vote
0answers
67 views

R plm cluster robust standard errors with multiple imputations

I am looking for a way to implement (country) clustered standard errors on a panel regression with individual fixed effects. That is, in plm() I want to define some ...
0
votes
1answer
23 views

Diff in Diff contradicting results with daily and weekly data

I am trying to analyse an experiment where in one region a treatment was given and in three other regions no treatment was given (control group). I have daily panel data for each region over a course ...
0
votes
1answer
52 views

Placebo test for the validity of difference-in-differences analysis results for limited data period

I am doing an analysis of a strategy implemented by a four-year-old corporate company and this implementation was given in different cities which all of its employees were received the treatment or ...
1
vote
0answers
19 views

Difference in estimates from regression on individual and aggregated data

I am trying to estimate a two-way fixed effects model: $$ y_{jt} = \alpha_j+\lambda_t+\tau D_{jt}+e_{jt} $$ Let's say $j$ is job, $t$ is time, $D_{jt}$ is some time-varying job characteristic, and $y_{...
1
vote
0answers
12 views

Validity of applying cross-section analyses to balanced panel data

(I apologize if this question is off-topic.) I would like to apply a method developed for time-series cross-section data to a balanced panel dataset to estimate the effect of a treatment. What I mean ...
2
votes
1answer
37 views

Synthetic Control Assumptions

I have recently started looking into the synthetic control method, and found it quite appealing. But it seems as some issues do not receive a formal definition (or at least I haven't found one): ...
0
votes
1answer
45 views

Why are coefficient and standard errors zero?

I am having a problem with OLS regression. I am doing a relative time model (leads and lags model) to prove the robustness of my Difference in differences model. Problem is that some of my ...
1
vote
1answer
100 views

Event study controlling for unit-specific linear time trends [closed]

I am running an event-study analysis. Is it possible to control for individual FE, year FE, and individual-specific linear time trends, and still obtain coefficients for every year? For example, I'd ...
1
vote
0answers
28 views

How to generate the leads and lags matrix for relative time models?

I have been struggling with this question for weeks. I would truly appreciate any sort of help. In my data, I have 150 individuals and 22 time periods (weekly data, so 22 weeks). The individuals are ...
0
votes
2answers
62 views

How to back transform ln + 1 or log10 + 1, and interpret that result?

I have some issues with my linear difference-in-difference analyses. My outcome is health care costs, where a lot of people have 0 costs and some have really high costs. Therefore, I logtransformed my ...
1
vote
2answers
95 views

Difference in difference with two treatment groups and one control group (Classification of control group)

I have an experiment which has 2 treatment groups (effects) and a control group. The treatment groups are not the same. If one belongs to the first treatment group it is not likely that one also ...
0
votes
0answers
8 views

Dummy Y variable and interaction effect

I am working on a project where I am studying the effect of a policy. There are 4 groups of people, male-control, female-control, male-treatment and female-treatment. I want to see if the difference ...
1
vote
0answers
34 views

How can my confidence interval and p-value not be in line with each other in a linear difference-in-difference analysis in R?

I'm performing a linear difference-in-difference analysis with mental health care costs, log transformed (log10), as outcome measurement. Individuals are placed in a treatment or control group, and I ...
0
votes
2answers
33 views

Difference-in-difference-in-difference using time-series data of unemployment rate testing for changes in rate after policy measure

Is it possible to make a difference-in-difference-in-difference model with time-series data of unemployment rate for one country (where groups=3 different time periods) testing for changes in rate ...
0
votes
0answers
13 views

Treatment effect by regression slope in simulated A/A-test

Sometimes when doing A/B-test, I see a difference between control and test groups before experiment. I want to decide whether or not subtract this diff from the diff after the experiment (diff-in-diff)...
0
votes
0answers
10 views

Sample size calculation for Difference in difference

We are planning to launch a causal experiment - in which one group gets t (treatment), while the other group gets c (control). So assuming that we have our pre launch number in each group (denoted by ...
0
votes
0answers
18 views

Difference in difference in means

I am working on an experiment with the following setup-- I have divided 160 people into two groups based on gender. There are 70 females and 90 males. Then, in the female group, I have on the basis ...
1
vote
1answer
53 views

How is it decided to use Difference in Differences, Regression Discontinuity or both together (if possible) according to the policy change?

I am quite new at (quasi) natural experiment analysis, so please bear with me, and got some questions. In my research, I am planning to use one policy change which happened 2002 and treated firms are ...
0
votes
1answer
27 views

Difference in difference with delayed effect

Imagine I have a policy intervention where I expect a one-period lag between when the intervention happens and when the intervention's effect shows up in my outcome variable. Something slow to adjust, ...
0
votes
0answers
44 views

Difference in differences - Is it OK to use the same variable to define the treat group and inside the regression?

I'm running diff and diff regression using the results of a repeated cross-sectional survey. I'm trying to test the effects of raise in min wage. I didn't have the actual salaries of the people who ...
0
votes
0answers
31 views

Looking for feedback on matching and difference-in-differences analysis

I am looking to set up my data and I have a question about the matched-pairs approach. I have plans for how to setup my data and am hoping for feedback as to whether it is a good way to go. ...
0
votes
0answers
33 views

Is this a valid differences-in-differences-in-differences design?

I'm interesting in exploiting policy changes in benefits enjoyed by individuals to estimate the effect of the benefit on a certain outcome variable. The policy changes come in the following form: at ...
2
votes
1answer
228 views

Staggered Diff-in-Diff: multiple treatments equation

I wonder if you can help me to figure out how to rewrite basic difference-in-difference equation (pictured) so that it takes into account the fact that treatment has occurred at different times for ...

1
2 3 4 5
9