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# Re: st: Event study

 From Nick Cox To "statalist@hsphsun2.harvard.edu" Subject Re: st: Event study Date Fri, 12 Apr 2013 14:05:31 +0100

Should be

egen benchmark = total(abnormalreturn / (day == -1)), by(country)
Nick
njcoxstata@gmail.com

On 12 April 2013 13:55, 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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