Specifying reference category for fixed effects

[Spencer Williams]

Hi Statalist,

I apologize in advance if this question has been covered before on another thread. I tried searching for a similar thread, but no luck.

I'm using fixed effects as part of a number of different regression specifications such as OLS, probit, logit, etc. I have a number of variables that I am controlling for using fixed effects. For example, I have a variable called "industry" for which there are observations such as "Life Sciences," "Software," etc.

When I run a regression and use fixed effects (i.industry), Stata automatically chooses a category (such as "Life Sciences") to drop from the regression as the reference category. Is there a way to specify which category is used as the reference category?

Thanks for the help.

Spencer

[Andrew Castro]

Yes, this is known as "Specifying base levels." See here for a complete guide: http://www.stata.com/manuals13/u11.p....3.2Baselevels

[daniel klein]

Note that including indicator variables is equivalent to the within-estimator only in the case of OLS. In the non-linear case fixed-effects are usually estimated via conditional (likelihood) models and not numerically identical to the inclusion of indicators.

Best
Daniel

[Spencer Williams]

Thanks a lot Andrew and Daniel. This is very helpful.

Spencer