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Re: st: Programming a loop to exclude M&As in the 5 years prior to an M&A


From   "Austin Nichols" <austinnichols@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Programming a loop to exclude M&As in the 5 years prior to an M&A
Date   Thu, 16 Oct 2008 15:31:56 -0400

Pascal Stock <pstock@rumms.uni-mannheim.de>:
Is this the kind of thing you want?

clear
input acquiror_cusip target_cusip year_of_announcement
037833100 931142103 1990
037833100 931142102 1991
037833100 931142102 1997
331142103 131142102 1990
231142103 331142103 1993
931142103 231142102 1999
end
ren acquiror_cusip cusip0
ren target_cusip cusip1
ren year_of_announcement y
g i=_n
reshape long cusip, i(i) j(targ)
bys cusip (y): g dropme=y[_n+1]-y<=5
format cusip %12.0f
li, noo sepby(cusip)
egen todrop=max(dropme), by(i)
drop if todrop==1
drop dropme todrop
reshape wide cusip, i(i) j(targ)
ren cusip0 acquiror_cusip
ren cusip1 target_cusip
ren y year_of_announcement
sort i
drop i
li


On Thu, Oct 16, 2008 at 6:03 AM,  <pstock@rumms.uni-mannheim.de> wrote:
> Hello Statausers,
>
> I am new to STATA and try to program a screening loop to exclude from my SDC
> M&A sample those M&As in which the acquiror or target of an M&A in a
> particular year_of_announcement==`j' with j=1987-2006 has been the target or
> acquiror in an M&A in one of the preceeding 5 years. This screening is
> needed to avoid the problem of overlapping events in the analysis of the
> stock returns after the M&A.
>
> My problem is how to program that STATA is supposed to look in a particular
> year for all acquirors and targets that are acquirors or targets in one of
> the past 5 years. The target_cusip and acquiror_cusip as identifiers are
> organized in seperate colums. So STATA has to go through these two colums in
> each year and look for duplicated cusips that occur already in the
> year_of_announcement looked at.
>
> So far I programmed the following loop, but do not know how to indicate that
> the year_of_announcement==`j' is the base year from which Stata has to go
> back year by year to look for the cusips occuring in year j that are
> duplicated in the previous years :
>
> local j=1987
> forvalues j=1987/2006 {
>
>        drop if acquiror_cusip==acquiror_cusip & year_of_announcement==`j'-1
>        drop if acquiror_cusip==target_cusip & year_of_announcement==`j'-1
>        drop if target_cusip==target_cusip & year_of_announcement==`j'-1
>        drop if target_cusip==acquiror_cusip & year_of_announcement==`j'-1
>
>        drop if acquiror_cusip==acquiror_cusip & year_of_announcement==`j'-2
>        drop if acquiror_cusip==target_cusip & year_of_announcement==`j'-2
>        drop if target_cusip==target_cusip & year_of_announcement==`j'-2
>        drop if target_cusip==acquiror_cusip & year_of_announcement==`j'-2
>
>        drop if acquiror_cusip==acquiror_cusip & year_of_announcement==`j'-3
>        drop if acquiror_cusip==target_cusip & year_of_announcement==`j'-3
>        drop if target_cusip==target_cusip & year_of_announcement==`j'-3
>        drop if target_cusip==acquiror_cusip & year_of_announcement==`j'-3
>
>        drop if acquiror_cusip==acquiror_cusip & year_of_announcement==`j'-4
>        drop if acquiror_cusip==target_cusip & year_of_announcement==`j'-4
>        drop if target_cusip==target_cusip & year_of_announcement==`j'-4
>        drop if target_cusip==acquiror_cusip & year_of_announcement==`j'-4
>
>        drop if acquiror_cusip==acquiror_cusip & year_of_announcement==`j'-5
>        drop if acquiror_cusip==target_cusip & year_of_announcement==`j'-5
>        drop if target_cusip==target_cusip & year_of_announcement==`j'-5
>        drop if target_cusip==acquiror_cusip & year_of_announcement==`j'-5
> }
>
> I gues a command with a varlist like forvalues j=1987/2006 of varlist
> year_of_announcement {.....}
>
> Kind regards
>
> Pascal Stock
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