st: looping

[Scott Cunningham <scunning@gmail.com>]

I have the following dataset:

perwt year state msa county males females age race

My goal is to create sex ratios (ie ratios of males to females) for  
each county.  I have not attempted this before because the way that I  
calculated sex ratios for states and cities (ie, msa) was to write  
a .do file that summed up the person weights (ie, perwt) for each  
state/msa.  This was not so bad for states, but moreso for cities,  
since there are 350 cities.  The number of counties are in the  
thousands, and since I have to create sex ratios that differ by race,  
age and year, it would require writing out a very long .do file.  So  
my question is:  is there a looping procedure I could use, which  
would use the county-level variable as the variable that does the  
operation?  For instance, if there were two counties (1 and 2), then  
the loop would sum all males of the given age-race criteria, all  
females of the same age-race criteria, take the ratio and record that  
for county 1, then repeat for county 2, etc.

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