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From |
Nick Cox <njcoxstata@gmail.com> |

To |
"statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |

Subject |
Re: st: RE: Does xtreg (or xtivreg) assume equally spaced time points?p |

Date |
Tue, 7 Aug 2012 18:00:15 +0100 |

Hi Mark,Thank you for your response. Our data are in long format with fourlines per person (one line for each time point).I think we should add ", i(id)" at the end of our model.I think I forgot that. Time points are nested within persons, soonce we add the code above, it will have a time dimension.However, the time points are not equally spaced. How can we accountfor that in an xtivreg model?Thanks for your help, Lisa ----- Original Message ----- From: "Schaffer, Mark E" <M.E.Schaffer@hw.ac.uk> To: statalist@hsphsun2.harvard.edu Cc: Sent: Tuesday, August 7, 2012 8:27 AMSubject: st: RE: Does xtreg (or xtivreg) assume equally spaced timepoints?Lisa, The model you specify below,Our model is: xtivreg depper (bmi = momobes)has no apparent time dimension, i.e., it seems to be a staticmodel. Ifso, the spacing between consecutive periods is irrelevant and youdon'tneed to do anything. HTH, Mark-----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner- statalist@hsphsun2.harvard.edu] On Behalf Of Lisa Marie Yarnell Sent: 07 August 2012 15:32 To: statalist@hsphsun2.harvard.edu Subject: st: Does xtreg (or xtivreg) assume equally spaced timepoints?Hi Statalisters, Does xtreg (or really, what we are using, xtivreg--the extension ofxtreg thatallows for an instrument) asusme equally-spaced time points in thepanelmodel? We have four waves of data. Wave I and Wave II are 1.5 years apart. Wave II and Wave III are 5.5 years apart. Wave III and Wave IV are 6 years apart.Is it wrong to put data from these time points into the xtivregmodel?Isthere a way to adjust the model for unequally spaced time points? Our model is: xtivreg depper (bmi = momobes) How can we alter the model to account for the unequal spacing?

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**References**:**st: IV with many fixed effects***From:*Francie Streich <francie.streich@gmail.com>

**st: RE: IV with many fixed effects***From:*"Schaffer, Mark E" <M.E.Schaffer@hw.ac.uk>

**Re: st: RE: IV with many fixed effects***From:*Francie Streich <francie.streich@gmail.com>

**st: Does xtreg (or xtivreg) assume equally spaced time points?***From:*Lisa Marie Yarnell <lisayarnell@yahoo.com>

**st: RE: Does xtreg (or xtivreg) assume equally spaced time points?***From:*"Schaffer, Mark E" <M.E.Schaffer@hw.ac.uk>

**st: RE: Does xtreg (or xtivreg) assume equally spaced time points?***From:*Lisa Marie Yarnell <lisayarnell@yahoo.com>

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