st: Identifying single psu within strata

["R.E. De Hoyos" <redeho@hotmail.com>]

Statalist,

I want to run wage regressions for several population groups. Estimations 
have to take care of the survey design (svy). The problem is that for some 
of the groups there are strata with a single psu (primary samplying unit). 
Using -svydes- I can identify does strata, for example:

For wage equation: svyreg wage_1 varlist_1:

svydes wage_1 varlist_1

And Stata will highlight those strata with a single psu. How can I create a 
dummy variable that indicates weather a strata has a single psu given the 
variables that I want to use for the analysis?
In other words I want a dummy variable that takes the value of 1 if -svydes- 
highlights a strata.

Rafa 
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