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From |
Nyasha Tirivayi <ntirivayi@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: AW: mfx-Elasticity for a dummy variable |

Date |
Thu, 10 Jun 2010 18:09:13 +0200 |

Dear Antonis Yes you have the model correct. However, you earlier said the elasticity was c*T instead of c/T. Which is it then? Kindly advise Regards Nyasha Tirivayi Maastricht University On Thu, Jun 10, 2010 at 11:11 AM, A Loumiotis <antonis.loumiotis@gmail.com> wrote: > your model is (correct me if i'm wrong): > > ln(y) = a + b ln(x) + c T + dZ + error > > The elasticity of y with respect to T is > (dy/y)/(dT/T)=dln(y)/(dT/T)=(dln(y)/dT)/T=c/T. > > So, the elasticity of y with respect to T does not depend on the means > of ln(x) and ln(y). As I said in my previous reply it is equal to the > coefficient of the dummy variable T divided by T (= c / T). So the > elasticity will be equal to "c" only if you calculate it at T=1 and > not at the mean of T. It is your call but you should consider the > drawbacks of computing elasticities with respect to dummy(discrete) > variables. > > Antonis > > On Wed, Jun 9, 2010 at 6:15 PM, Nyasha Tirivayi <ntirivayi@gmail.com> wrote: >> Dear Antonis and Martin >> >> Thanks for your reply. If you recall my model is as follows: >> >> ln(y) = a + b ln(x) + T + D Z >> >> I intend to calculate elasticity for T at T=1 and at means of ln(x) >> and ln(Y). And if I do that the elasticity is the same as the >> coefficient of T. >> >> Should I proceed with that as the answer? >> >> Kindly advise >> >> Nyasha Tirivayi >> Maastricht University >> >> On Tue, Jun 8, 2010 at 1:27 PM, A Loumiotis <antonis.loumiotis@gmail.com> wrote: >>> Yes I agree... although one can compute it at the mean point of T >>> which is different from 0 or 1. But as I said in my first response >>> elasticities with respect to dummy variables have no meaningful >>> interpretation. >>> >>> On Tue, Jun 8, 2010 at 2:18 PM, Martin Weiss <martin.weiss1@gmx.de> wrote: >>>> >>>> <> >>>> >>>> " ...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 >>>>>>> * >>>>>>> * For searches and help try: >>>>>>> * http://www.stata.com/help.cgi?search >>>>>>> * http://www.stata.com/support/statalist/faq >>>>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>>>> >>>>>>> >>>>>>> * >>>>>>> * For searches and help try: >>>>>>> * http://www.stata.com/help.cgi?search >>>>>>> * http://www.stata.com/support/statalist/faq >>>>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>>>> >>>>>> >>>>>> * >>>>>> * For searches and help try: >>>>>> * http://www.stata.com/help.cgi?search >>>>>> * http://www.stata.com/support/statalist/faq >>>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>>> >>>>> >>>> >>>> * >>>> * For searches and help try: >>>> * http://www.stata.com/help.cgi?search >>>> * http://www.stata.com/support/statalist/faq >>>> * http://www.ats.ucla.edu/stat/stata/ >>>> >>>> >>>> * >>>> * For searches and help try: >>>> * http://www.stata.com/help.cgi?search >>>> * http://www.stata.com/support/statalist/faq >>>> * http://www.ats.ucla.edu/stat/stata/ >>>> >>> >>> * >>> * For searches and help try: >>> * http://www.stata.com/help.cgi?search >>> * http://www.stata.com/support/statalist/faq >>> * http://www.ats.ucla.edu/stat/stata/ >>> >> >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/statalist/faq >> * http://www.ats.ucla.edu/stat/stata/ >> > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: AW: mfx-Elasticity for a dummy variable***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**References**:**st: mfx-Elasticity for a dummy variable***From:*Nyasha Tirivayi <ntirivayi@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*Nyasha Tirivayi <ntirivayi@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*Nyasha Tirivayi <ntirivayi@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*A Loumiotis <antonis.loumiotis@gmail.com>

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