st: Event study 300 companies using a SUR to estimate standard market models

[Doryon Zalko <u4221483@anu.edu.au>]

Hi,

I am conducting an event study on each stock in the ASX 300 using the standard market model. I am using  an estimation period of 100 days, and a period before the event window of 40 days. 

I need to use a seemingly unrelated regression for estimating the 300 standard market models. But I am having trouble programming Stata to run SUR during the estimation period and then predict the abnormal return over the event window all at once.

Is this even possible? If so how would I go about it?


Prior to using SUR I was estimating the standard market model using a doloop:

gen predicted_return=.

egen id=group(gvkey)

 forvalues i=1(1)300 {

        regress stockreturn ri if id==`i' & EP1==1

        predict p if id==`i'

        replace predicted_return = p if id==`i' & event1==1

        drop p

}

sort id event1 datadate

gen abnormal_return=stockreturn-predicted_return if event1==1

sort id event1 datadate

by id: egen cumulative_abnormal_return= sum(abnormal_return)

sort id datadate

by id: egen ar_sd= sd(abnormal_return)

gen testew =(1/sqrt(5)) * ( cumulative_abnormal_return /ar_sd)

drop predicted_return abnormal_return 


Where, EP1 and event1 variables taking on the value of 0 or 1. For EP1,  1 for estimation period, 0 otherwise.
For event1, 1 for event window, 0 otherwise.

Is it possible to adapt this into the seemingly unrelated regression code? Hints would be appreciated.


Thanks for your help