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RE: st: RE: RE: xtivreg2 -- Instruments dropped


From   "Schaffer, Mark E" <[email protected]>
To   <[email protected]>
Subject   RE: st: RE: RE: xtivreg2 -- Instruments dropped
Date   Sun, 16 Jan 2011 22:43:16 -0000

Actually, I was wrong (sort of) - it turns out the "space" before the comma in Ivan's email wasn't an ascii space (32), it was an extended ascii non-breaking space (160).  Get rid of that and both -xtivreg2- and -xtivreg- work fine with Ivan's data and estimation, as far as I can tell.

--Mark

> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf Of DE 
> SOUZA Eric
> Sent: 16 January 2011 14:38
> To: [email protected]
> Subject: RE: st: RE: RE: xtivreg2 -- Instruments dropped
> 
> So the space before the comma was the reason I couldn't get 
> it to run this time. I saw the error message but then had to 
> move on something else.
> 
> Eric
> 
> 
> Eric de Souza
> College of Europe
> Brugge (Bruges), Belgium
> http://www.coleurope.eu
> 
> 
> 
> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf Of 
> Schaffer, Mark E
> Sent: 16 January 2011 15:30
> To: [email protected]
> Subject: RE: st: RE: RE: xtivreg2 -- Instruments dropped
> 
> Ivan,
> 
> I used your corrected dataset, and made some progress in 
> tracking down the problem, but there are still aspects I 
> don't understand.
> 
> 1.  Easy part: to identify your versions of xtivreg2, ivreg2, 
> xtivreg, etc., you use the -which- command.  It's best to use 
> the -all- option with it, in case there are multiple versions 
> lurking on your machine.  For example,
> 
> . which xtivreg, all
> 
> C:\Program Files\Stata11\ado\updates\x\xtivreg.ado
> *! version 1.5.9  11nov2009
> 
> C:\Program Files\Stata11\ado\base\x\xtivreg.ado
> *! version 1.5.7  17jun2009
> 
> NB: The dulpicate versions above aren't a problem for an 
> official program like -xtivreg-.  When you update your Stata 
> and a do file gets updated, the update goes in the updates 
> folder and the original stays in the base folder.
> 
> 2.  I can't run your example, using either -xtivreg2- or 
> official -xtivreg-.  The reason is a bug, or perhaps 
> "inflexibility", in the parsing done by -xtivreg2- and 
> -xtivreg-.  It is very simple: if you use a space between the 
> end of an -if- statement and the comma, both -xtivreg2- and 
> -xtivreg- complain in a very uninformative way:
> 
> First, -xtivreg2-:
> 
> . xi: xtivreg2 xrdr_ln revtr_ln mktbook_mm ebitdar_ln     ///
> >         taxcred (L.utsa = L.govr_r) i.year ///
> >         if xrdr_count >= 6  , fe cluster(state_sic)
> i.year            _Iyear_1976-2006    (naturally coded; 
> _Iyear_1976 omitted)
> 6  invalid name
> r(198);
> 
> end of do-file
> 
> r(198);
> 
> Now official -xtivreg-:
> 
> . xi: xtivreg xrdr_ln revtr_ln mktbook_mm ebitdar_ln      ///
> >         taxcred (L.utsa = L.govr_r) i.year ///
> >         if xrdr_count >= 6  , fe cluster(state_sic)
> i.year            _Iyear_1976-2006    (naturally coded; 
> _Iyear_1976 omitted)
> 6  invalid name
> r(198);
> 
> end of do-file
> 
> r(198);
> 
> But delete the spaces between 6 and the comma, and it works:
> 
> . xi: xtivreg2 xrdr_ln revtr_ln mktbook_mm ebitdar_ln     ///
> >         taxcred (L.utsa = L.govr_r) i.year ///
> >         if xrdr_count >= 6, fe cluster(state_sic)
> i.year            _Iyear_1976-2006    (naturally coded; 
> _Iyear_1976 omitted)
> Warning - singleton groups detected.  295 observation(s) not used.
> Warning - collinearities detected
> Vars dropped:  _Iyear_2006
> 
> FIXED EFFECTS ESTIMATION
> ------------------------
> Number of groups =      3198                    Obs per 
> group: min =         2
>                                                               
>  avg =       8.5
>                                                               
>  max =        30
> 
> IV (2SLS) estimation
> --------------------
> 
> Estimates efficient for homoskedasticity only Statistics 
> robust to heteroskedasticity and clustering on state_sic
> 
> Number of clusters (state_sic) =   1471               Number 
> of obs =    27044
>                                                       F( 34,  
> 1470) =     3.85
>                                                       Prob > 
> F      =   0.0000
> Total (centered) SS     =  251.0415486                
> Centered R2   =   0.2476
> Total (uncentered) SS   =  251.0415486                
> Uncentered R2 =   0.2476
> Residual SS             =  188.8924922                Root 
> MSE      =     .089
> 
> --------------------------------------------------------------
> ----------------
>              |               Robust
>      xrdr_ln |      Coef.   Std. Err.      z    P>|z|     
> [95% Conf. Interval]
> -------------+------------------------------------------------
> ----------
> -------------+------
>         utsa |
>          L1. |   .0174583   .0902999     0.19   0.847    
> -.1595263    .1944429
>              |
>     revtr_ln |   .1265504   .0205411     6.16   0.000     
> .0862907    .1668102
>   mktbook_mm |   .0149745   .3796314     0.04   0.969    
> -.7290894    .7590385
>   ebitdar_ln |   .0408917   .0159209     2.57   0.010     
> .0096873    .0720961
>      taxcred |  -.1079932   .5174864    -0.21   0.835    
> -1.122248    .9062615
>  _Iyear_1977 |  -.0313348   .0448701    -0.70   0.485    
> -.1192785     .056609
> ...
> <output edited for brevity>
> ...
>  _Iyear_2005 |  -.0105457   .0033898    -3.11   0.002    
> -.0171896   -.0039017
> --------------------------------------------------------------
> ----------------
> Underidentification test (Kleibergen-Paap rk LM statistic):   
>           46.831
>                                                    Chi-sq(1) 
> P-val =    0.0000
> --------------------------------------------------------------
> ----------------
> Weak identification test (Cragg-Donald Wald F statistic):     
>          202.397
>                          (Kleibergen-Paap rk Wald F 
> statistic):         53.412
> Stock-Yogo weak ID test critical values: 10% maximal IV size  
>            16.38
>                                          15% maximal IV size  
>             8.96
>                                          20% maximal IV size  
>             6.66
>                                          25% maximal IV size  
>             5.53
> Source: Stock-Yogo (2005).  Reproduced by permission.
> NB: Critical values are for Cragg-Donald F statistic and 
> i.i.d. errors.
> --------------------------------------------------------------
> ----------------
> Hansen J statistic (overidentification test of all 
> instruments):         0.000
>                                                  (equation 
> exactly identified)
> --------------------------------------------------------------
> ----------------
> Instrumented:         L.utsa
> Included instruments: revtr_ln mktbook_mm ebitdar_ln taxcred 
> _Iyear_1977 ...
> <output edited for brevity>
> ...                      _Iyear_2002 _Iyear_2003 _Iyear_2004 
> _Iyear_2005
> Excluded instruments: L.govr_r
> Dropped collinear:    _Iyear_2006
> --------------------------------------------------------------
> ----------------
> 
> 3.  I still don't understand what you mean when you say
> 
> > IP: I meant instruments -- in the sense that I used different 
> > instruments in various specifications, and each one was dropped.
> 
> I'm pretty sure you don't mean that -xtivreg2- drops every 
> excluded instrument but still reports a coefficient for an 
> endogenous regressor!  But then, what do you mean?
> 
> But maybe it doesn't matter if simply eliminating the spaces 
> between 6 and the comma solves your problem.
> 
> Best wishes,
> Mark
> 
> > -----Original Message-----
> > From: [email protected]
> > [mailto:[email protected]] On Behalf Of Ivan Png
> > Sent: 16 January 2011 03:25
> > To: [email protected]
> > Subject: Re: st: RE: RE: xtivreg2 -- Instruments dropped
> > 
> > Sorry, Mark.  I've updated the data-set.
> > 
> > On Sat, Jan 15, 2011 at 10:29 PM, Schaffer, Mark E 
> > <[email protected]> wrote:
> > > Ivan,
> > >
> > > I had the same problem as Eric.  And there must be
> > something else wrong, since there's only one instrument listed
> > (L.govr_r) and you refer to "instruments".
> > >
> > 
> > IP: I meant instruments -- in the sense that I used different 
> > instruments in various specifications, and each one was dropped.
> > 
> > > Did xtivreg2 report collinearities among your instruments
> > as a reason for dropping some?  Did xtivreg?  If so, were 
> the dropped 
> > variables the same?
> > 
> > IP; Neither reported collinearities.
> > 
> > > You might also want to compare the first-stage regressions
> > of xtivreg2 and xtivreg.
> > >
> > > Oh, and tell us which versions of xtivreg2, xtivreg and
> > Stata you are using.
> > 
> > IP: Stata/IC 10.1.  Sorry, please advise how to identify version of
> > xtivreg2 and xtivreg
> > 
> > 
> > > --Mark
> > >
> > >> -----Original Message-----
> > >> From: [email protected]
> > >> [mailto:[email protected]] On Behalf Of
> > DE SOUZA
> > >> Eric
> > >> Sent: 15 January 2011 12:02
> > >> To: [email protected]
> > >> Subject: st: RE: xtivreg2 -- Instruments dropped
> > >>
> > >> Check the instruction you have posted:
> > >> govr_r does not exist
> > >>
> > >>
> > >>
> > >> Eric de Souza
> > >> College of Europe
> > >> Brugge (Bruges), Belgium
> > >> http://www.coleurope.eu
> > >>
> > >>
> > >> -----Original Message-----
> > >> From: [email protected]
> > >> [mailto:[email protected]] On Behalf 
> Of Ivan Png
> > >> Sent: 15 January 2011 12:43
> > >> To: [email protected]
> > >> Subject: st: xtivreg2 -- Instruments dropped
> > >>
> > >> Dear Stata-list:
> > >>
> > >> I'm having difficulty with xtivreg2
> > >>
> > >> Each time, the system drops the instruments for the
> > variable L.utsa.
> > >> utsa is a state-time variable that varies across states
> > and times. I
> > >> checked the instruments: they are state- and time-varying.
> >   I don't
> > >> understand why the system drops the instruments.  (I 
> tried xtivreg 
> > >> and it works, but I would like to use xtivreg2 so that I can get 
> > >> cluster standard errors and the diagnostics for weak 
> instruments).
> > >>
> > >>
> > >> Please help.  Many thanks!
> > >>
> > >> Data-set:
> > >> http://www.comp.nus.edu.sg/~ipng/research/company_wrkg.dta
> > >>
> > >>
> > >> Code:
> > >> . xtset gvkey year
> > >>
> > >> . xi: xtivreg2 xrdr_ln revtr_ln mktbook_mm ebitdar_ln taxcred ///
> > >>     (L.utsa = L.govr_r) i.year trend_AL - trend_WY ///
> > >>     if xrdr_count >= 6  , fe cluster(state_sic)
> > >>
> > >>
> > >>
> > >>
> > >> --
> > >> Ivan Png
> > >> National U of Singapore
> > >>
> > >>
> > >>
> > >>
> > >> --
> > >> Skype: ipng00
> > >> T: +65 6516 6807
> > >>
> > >>
> > >>
> > >> --
> > >> Skype: ipng00
> > >> T: +65 6516 6807
> > >>
> > >> *
> > >> *   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/
> > >>
> > >
> > >
> > > --
> > > Heriot-Watt University is a Scottish charity registered
> > under charity
> > > number SC000278.
> > >
> > >
> > > *
> > > *   For searches and help try:
> > > *   http://www.stata.com/help.cgi?search
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> > > *   http://www.ats.ucla.edu/stat/stata/
> > >
> > 
> > 
> > 
> > --
> > Skype: ipng00
> > T: +65 6516 6807
> > 
> > *
> > *   For searches and help try:
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> > *   http://www.stata.com/support/statalist/faq
> > *   http://www.ats.ucla.edu/stat/stata/
> > 
> 
> 
> --
> Heriot-Watt University is a Scottish charity registered under 
> charity number SC000278.
> 
> 
> *
> *   For searches and help try:
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> 
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> 


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