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AW: st: AW: mfx-Elasticity for a dummy variable


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   AW: st: AW: mfx-Elasticity for a dummy variable
Date   Tue, 8 Jun 2010 13:18:30 +0200

<> 

" ...will be the coefficient of the dummy
 variable T divided by the dummy variable itself."


I do not get this sentence. The dummy is either 0 or 1, as you said.
Dividing by zero is not permissible, and dividing by one does not change
anything, does it?



HTH
Martin

-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von A Loumiotis
Gesendet: Dienstag, 8. Juni 2010 13:15
An: statalist@hsphsun2.harvard.edu
Betreff: Re: st: AW: mfx-Elasticity for a dummy variable

 The elasticity of y with respect to the dummy variable in the way that
 you have defined your regression will be the coefficient of the dummy
 variable T divided by the dummy variable itself.

On Tue, Jun 8, 2010 at 2:05 PM, A Loumiotis <antonis.loumiotis@gmail.com>
wrote:
> Nyasha,
>
> The elasticity of y with respect to the dummy variable in the way that
> you have defined your regression will be the coefficient of the dummy
> variable T times the dummy variable itself.  If you calculate it at
> the mean point of T then it will be different from the coefficient of
> the dummy variable.  If you calculate it at T=1, it will be the same.
>
> However elasticities with respect to dummy variables have no
> meaningful interpretation because the dummy variable changes in a
> discrete fashion (from 0 to 1).
>
> Antonis Loumiotis
>
> On Mon, Jun 7, 2010 at 6:24 PM, Nyasha Tirivayi <ntirivayi@gmail.com>
wrote:
>> Dear Martin
>>
>> Thanks for the code. Now the results are different. I was using the
>> wrong code i.e mfx , dyex at(mean) instead of mfx compute,
>> varlist(logweight) dyex at(mean).
>>
>> Regards
>>
>> Nyasha Tirivayi
>> Maastricht University
>>
>>
>>
>> On Mon, Jun 7, 2010 at 9:16 AM, Martin Weiss <martin.weiss1@gmx.de>
wrote:
>>>
>>> <>
>>>
>>> What is the difference of your example to this one - where the marginal
>>> effects do seem to change:
>>>
>>>
>>> *************
>>> sysuse auto, clear
>>> gen logprice=log(price)
>>> gen logweight=log(weight)
>>> reg logprice length logweight foreign
>>> mfx compute, varlist(logweight) dydx at(mean)
>>> mfx compute, varlist(logweight) eyex at(mean)
>>> mfx compute, varlist(logweight) dyex at(mean)
>>> mfx compute, varlist(logweight) eydx at(mean)
>>> *************
>>>
>>>
>>>
>>> HTH
>>> Martin
>>>
>>> -----Ursprüngliche Nachricht-----
>>> Von: owner-statalist@hsphsun2.harvard.edu
>>> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Nyasha
Tirivayi
>>> Gesendet: Montag, 7. Juni 2010 02:50
>>> An: statalist@hsphsun2.harvard.edu
>>> Betreff: st: mfx-Elasticity for a dummy variable
>>>
>>> Dear All
>>>
>>> I am trying to estimate elasticity for a dummy explanatory variable in
>>> the following model
>>>
>>> ln(y) = a + b ln(x) + T + D Z
>>>
>>>
>>>
>>> I am interested in calculating the elasticity for T a dummy variable
>>> for a "treatment". What is the formula in stata? Is it mfx,dy/dx or
>>> mfx,dyex?
>>>
>>>
>>>
>>> I have done mfx,dyex and the result still remains the coefficient for
>>> T. Could it be that simple? Or there is another way ?
>>>
>>>
>>>
>>> Kindly advise
>>>
>>>
>>>
>>> Nyasha Tirivayi
>>>
>>> Maastricht University
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>>
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>

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