Hello Stata Forum,

I am having trouble to understand my identifier and relate with fixed effects estimation. I have a database on beverages by brand, size (ml, liter, pack) and by city. So, in order to have an identifier I use:

egen pan_id = group(brand size city)

However, I would like to understand if this captures the time-invariant effects, such as city fixed effects, brand fixed effects, and size fixed effects. I am not sure because when I run an areg with dummy variables with each of this item separately I get different results, but when I absorb the pan_id variable, I get the same result so I am a bit confused what the difference is.

Thank you so much for your help. I really appreciate it.

Best,

Helena