st: perform regression on minimum number of observations stata

[Nahla Betelmal <nahlaib@gmail.com>]

Hi Statalist,

my data consists of several years and several industries (each
industry contain several firms). I run  cross-sectional regressions as
follow :

forval y=1989/2012 {
      forval  i= 1/57 {
           reg DV IV_1 IN_2 IN_3 if  Industry== `i' & year==`y'
}

I have two questions please:

1- According to literature, any industry-year regression with less
than 15 observations (i.e. 15 firms) should be disregarded. the tricky
thing is that almost every industry-year group has more than 15 firms
but some are with missing values to perform the regression. Therefore,
the regression could be done with less than 15 observation. How can I
account for this in the above loop, so regression with less than 15
complete observations produce missing values instead of actual values!

2- the output does not provide information about the matched year and
industry. Is there a way to do it?  I only need that for reporting
purpose.

Thank you

Nahla Betelmal
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