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From |
Austin Nichols <austinnichols@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: -gmm- and -outreg2- |

Date |
Fri, 17 Aug 2012 11:21:15 -0400 |

Joseph Monte <hmjc66@gmail.com> The log of E(y|X) is not the same as E(log y|X). -ivpois- assumes E(y|X)=exp(Xb) or log E(y|X) = Xb but your -ivreg2- call assumes E(log Y|X)=Xb which makes no sense when Y can take on the value zero, and generically gives different estimates. See also http://blog.stata.com/2011/08/22/use-poisson-rather-than-regress-tell-a-friend/ http://www.stata.com/meeting/boston10/boston10_nichols.pdf -ivpois- is only obsolete because you can use official -gmm- to get the same answer; -ivpois- can still be used if you prefer the output. If it is helpful to people, I could modify -ivpois- to use -gmm- and return estimates in a friendlier way when run on version 11 or higher. On Fri, Aug 17, 2012 at 8:42 AM, Joseph Monte <hmjc66@gmail.com> wrote: > Thanks, Scott. I need to read up on -gmm- as my question (resulting > from ignorance) pertained more to why the output using -gmm- and > -ivreg2- were different rather than the horizontal display of the > output using -gmm-. > > Joe > > On Wed, Aug 15, 2012 at 6:38 PM, Scott Merryman > <scott.merryman@gmail.com> wrote: >> Perhaps I am not following, but in the first example -outreg2- (-ssc >> desc outreg2-) is outputting the results from -gmm- and the in second >> example it is outputting the results from -ivreg2- (-ssc desc >> ivreg2-). Given that there are 17 equations in the gmm estimated >> model and -outreg2-, by default, outputs each equation in a separate >> column makes the display different than the output from -ivreg2-. >> Perhaps you want -onecol- option on -outreg2-? >> >> Scott >> >> >> On Wed, Aug 15, 2012 at 9:54 AM, Joseph Monte <hmjc66@gmail.com> wrote: >>> Richard, >>> >>> Here is an example:- >>> >>> use http://fmwww.bc.edu/ec-p/data/wooldridge/card, clear >>> loc x "exper* smsa* south mar black reg662-reg669" >>> ivpois wage `x', endog(educ) exog(nearc2 nearc4) >>> gmm (wage*exp(-{xb:`x' educ}-{b0})-1), inst(`x' nearc2 nearc4) >>> outreg2 using myfile, replace excel >>> >>> Is this how it is supposed to display? This output display is >>> different from the one below. >>> >>> use http://fmwww.bc.edu/ec-p/data/wooldridge/card, clear >>> loc x "exper* smsa* south mar black reg662-reg669" >>> ivpois wage `x', endog(educ) exog(nearc2 nearc4) >>> gmm (wage*exp(-{xb:`x' educ}-{b0})-1), inst(`x' nearc2 nearc4) >>> estat overid >>> ivreg2 lw `x' (educ=nearc2 nearc4) >>> outreg2 using myfile, replace excel >>> >>> Thanks, >>> >>> Joe * * 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/

**References**:**Re: st: -gmm- and -outreg2-***From:*Richard Williams <richardwilliams.ndu@gmail.com>

**Re: st: -gmm- and -outreg2-***From:*Joseph Monte <hmjc66@gmail.com>

**Re: st: -gmm- and -outreg2-***From:*Scott Merryman <scott.merryman@gmail.com>

**Re: st: -gmm- and -outreg2-***From:*Joseph Monte <hmjc66@gmail.com>

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