Hi All,

I am making use of the wonderful command
Code:
ppmlhdfe
which is used to estimate models with a large number of fixed effects using Poisson pseudo ML. One issue from the documentation (http://scorreia.com/help/ppmlhdfe.html) is that I am unable to find what the normalization was done for the reference category. I cannot tell, if a category is automatically dropped, or if there is some other constraint imposed, such as the sum of the fixed effects equalling 0. Any help on this is much appreciated.


Best,
CS