st: vce(analytic) for proportions-- what is it exactly?

["Tamer Farag" <tfarag@medicine.umaryland.edu>]

Hello All,
 
I am calculating survey weighted proportions using the svy: proportion command.  The Stata help file states that the default for calculating variance is vce(analytic).  Link below of the stata help file for proportion:
 
http://www.stata.com/help.cgi?proportion 
 
Specifically, it states:  
 

 ----+ SE/Cluster +-------------------------------------------------------
 vce(vcetype) specifies the type of standard error reported, which
        includes types that are derived from asymptotic theory, that allow
        for intragroup correlation, and that use bootstrap or jackknife
        methods; see [R]  ( http://www.stata.com/help.cgi?vce_option )vce_option ( http://www.stata.com/help.cgi?vce_option ).
 vce(analytic), the default, uses the analytically derived variance
        estimator associated with the sample proportion.
 
But just what is an "analytically derived variance estimator", exactly?  Is there any reason not to use it?
 
Many thanks,
Tamer
 
 

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