Hi,

I am estimating a firm group-level variable using a panel data set.
I have added fixed effects for time, industry, years and countries to account for any observed effects and used xtreg in the estimation.

However, my main independent variable is time-invariant. Therefore, I cannot estimate this within this model. I therefore consider using Pooled OLS for this estimation.

Now, I am rather confused about the difference in definition of both models.
Is a fixed effects model including time and firm fixed effects the same as Pooled OLS with time and firm dummies (and clustering errors)?


Assume the regression equation applying to this is Y = bX + error. Where X is time invariant and Y is time variant.

Can I add time dummies to this, or would this violate the Pooled OLS model?

best,
Frank