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Standard errors from did2s #13
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Actually, ignore my previous comment (I deleted it)! The difference between I'm not sure why gmm is producing smaller standard errors with |
Alright, for now simply say using group fixed effects may produce problems
right?
Thank you!
…On Tue, Mar 21, 2023 at 12:52 PM Kyle F Butts ***@***.***> wrote:
Actually, ignore my previous comment (I deleted it)! The difference
between did_imputation and did2s is due to using i.g in the first_stage
in the did2s call. Replacing that with i.i (which is what did_imputation)
uses produces ~ the same standard error.
I'm not sure why gmm is producing smaller standard errors with i.g, but
I'm pretty confident in the code. I just double checked all the theory and
the results match between Stata and R.
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Ahh, nope, the discrepancy is you are clustering on When you use group instead of individual fixed effects, the point estimate is the same (basically because the average of unit FEs in a group is equal to the group FE) but you're absorbing less variation so the standard errors are bigger. That's what you're seeing in the comparison of |
Hi Kyle
Not sure if you are still maintaining the program. But, while doing some notes on the methodology from scratch, i constructed a small dataset to run and try few commands (jwdid csdid did_impute and did2s).
The problem I find right now is that did2s does not seem to be providing the correct standard errors. They are, in fact, larger than the other estimators by far.
So, thinking about it again, I just went and constructed the GMM version of it, which produces the right numbers.
Would you mind taking a look and see what you think?
data:
SE using did2s
and using gmm:
which are very close to did_imputation
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