Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: RE: RE: estimation with a time trend.


From   natasha agarwal <agarwana2@googlemail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: RE: estimation with a time trend.
Date   Mon, 5 Jul 2010 15:34:49 +0100

On Mon, Jul 5, 2010 at 2:22 PM, Martin Weiss <martin.weiss1@gmx.de> wrote:
>
> <>
>
> The coeff for "t" will stay the same, then, no matter how you "center" it:
>
> *************
> use http://www.stata-press.com/data/r11/nlswork, clear
> egen t=group(year)
> xtreg  ln_wage wks_work tenure south nev_mar age t, fe vce(robust)
> replace t=t-7
> xtreg  ln_wage wks_work tenure south nev_mar age t, fe vce(robust)
> replace t=t-3
> xtreg  ln_wage wks_work tenure south nev_mar age t, fe vce(robust)
> *************

I tried this and as you said the coefficient stays the same. I was
wondering then what is the point in doing this then?

Thanks
Natasha

> HTH
> Martin
>
>
> -----Ursprüngliche Nachricht-----
> Von: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von natasha agarwal
> Gesendet: Montag, 5. Juli 2010 15:06
> An: statalist@hsphsun2.harvard.edu
> Betreff: Re: st: RE: RE: estimation with a time trend.
>
> On Mon, Jul 5, 2010 at 2:01 PM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
>> Your original question was
>>
>> "I was trying to estimate a production function with an unbalanced
>> firm-year panel data and wanted to include a time trend. However I was
>> not sure if the time trend was created correctly.
>>
>> egen t=group(year)
>>
>> I was wondering if anyone could please tell me if this was correct?"
>>
>> Who knows whether the commands you are using "mean center" the data if
>> you do not tell us what they are?
>
> I am sorry about this.
>
> I issue the following line of commands:
>
> egen t=group(year)
> xtreg lnrval lnk lnw lnvfdi t, fe vce(robust)
>
> Thanks
> Natasha
>
>
>
>
>
>> Nick
>> n.j.cox@durham.ac.uk
>>
>> natasha agarwal
>>
>> On Mon, Jul 5, 2010 at 1:14 PM, Maarten buis <maartenbuis@yahoo.co.uk>
>> wrote:
>>
>>> --- On Mon, 5/7/10, natasha agarwal wrote:
>>>> I am afraid I did not understand "year- (or -year-
>>>> MINUS> midpoint) for interpretability?"
>>>
>>> Say you have a variable representing year of birth
>>> ranging between 1910 and 1980. I would then usually
>>> have a line like this in my do-file:
>>>
>>> gen c_year = year - 1910
>>>
>>> Afterwards I would use c_year instead of year. In
>>> this case "midpoint" is 1910, and makes sure that
>>> your new variable is shifted to the left such that
>>> it has the value zero in 1910. This makes sure
>>> that the baseline in your models refer to a point
>>> at the beginning of your observed period. This is
>>> particularly important if you include interactions
>>> or if you care about the constant (e.g. in a random
>>> effects model)
>>
>> I am estimating the model with a within estimator. I thought that they
>> mean center the data anyways?
>>
>>
>> *
>> *   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/


© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   Site index