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Re: st: Event study


From   "Künzel Sven" <s.kuenzel@tu-braunschweig.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Event study
Date   Fri, 12 Apr 2013 15:08:35 +0200

I admit that "event study" is maybe not the right term for my problem.

For dissolving our confusion I want to calculate the change from day to day, so that the second example is the right one.

Thanks...

On Fri, 12 Apr 2013 13:55:49 +0100
 Nick Cox <njcoxstata@gmail.com> wrote:
I doubt that "event study" is universal jargon. Most things could qualify.

That aside, your example is not clear.

There are at least two things you can calculate, (1) change since time
datum and (2) change from day to day

The first is (for example)

egen benchmark = total(abnormalreturn / (day == -1)), by(country
gen deltachange = abnormalreturn - benchmark

and the second is

bysort country (day) : gen change = abnormalreturn - abnormalreturn[_n-1]

The variable -deltachange- you give seems to be one thing for some
observations and another thing for other observations, so at least one
of us is confused.

Nick
njcoxstata@gmail.com


On 12 April 2013 13:39, Künzel Sven <s.kuenzel@tu-braunschweig.de> wrote:

I am doing an Event-Study, which caused some troubles. In order to detect abnormal reactions between event day 0 and post-event day + 1 with the help of the event study, I want to compute the change between the days t and t-1.
Just below you see a data sample.

country  abnormalreturn day   DeltaChange
1              10        -2
1              11        -1       1
1              12        0        1
1              15        1        3
1              16        2        4
1              14        3        -2
1              13        4        -1
1              12        5        -1
2              35        -2
2              37        -1       2
2              39        0        2
2              32        1        -5
2              35        2        3
2              46        3        11
2              34        4        -12
2              37        5        +3

Is this possible? Which code would be the right one?

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