st: How to generate a dummy variable based on groups of variables in t-1

["Jean-Marie Meier" <jean-marie.meier@web.de>]

Dear Stata list,

It would be great if anyone could help me with this issue as I spent hours on it without solving it:

I have a dataset with all companys listed on US stock exchanges from 1979 up to now.
Every observation in my dataset are balance sheet and profit & loss account data for a given firm in a given year.

I have a dummy variable, which is 1 for an observation if a firm was taken over and left the dataset - e.g. firm ABC was taken over in 1985, then for all observations up to 1984 for this firm the dummy variable is 0 and for the observation in 1985 the dummy variable is 1. If a firm was not taken over, than the dummy variable is obviously always 0.

All firms/observations in my dataset are assigned an industry code between 1 and 48 (Fama French industry classification).

My problem now is:

How do I generate a dummy variable which is 1 for a given firm x and year t if there was a takeover in t-1 in the same industry (same industry code) and which is 0 otherwise ?

Looking forward to your answers

Kind regards,

Jean-Marie Meier
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