st: standard deviation around an event

["Khieu, Hinh" <Hdkhieu@usi.edu>]

Dear Statalist members,



I have a panel unbalanced data (firm ID, year, share issue year dummy, earnings). I need to calculate the standard deviation of earnings four years before share issue year and four years after share issue year. (I do not have the precise day and month of share issues; I only have year). I can certainly require my data have at least 9 consecutive observation years. That is, the standard deviation cannot include the year of the share issue. I do not know how to exclude that year from the standard deviation in STATA. Also, another problem is that sometimes firm can issue shares two or three years in a row.  In this case, I need to use only the four years before the first issue and the four years after the last consecutive share issue to calculate the standard deviation of earnings.



I would appreciate any amount of help to code this logic.



Thank you very much.



Regards,

Hinh

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