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From |
Estrella Gomez <estrellastata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: Dependent variable in a tobit model |

Date |
Mon, 15 Nov 2010 11:19:24 +0100 |

Dear Statalist: I am estimating a gravity equation of exports and I have decided to use tobit model, since the number of zeros in the dataset is high. This model is usually estimated in its loglinear version. However, if I use the logarithm of trade as dependent variable, the zeros are dropped (since the logarithm of zero is unfeasible). This is the command I have introduced in Stata 11: xttobit lxi lGDP_i lGDP_j contig comla smctry ldist RTAboth i.exporter i.importer i.year, ll(0) where "lxi" is the logarithm of exports and the independent variables are the standard variables in a gravity equation Of course, the number of censored observations is zero, since the dependent variable is introduced in logs. I think this is not correct, but I have seen this specification in most of the gravity-related articles Could somebody help me with this? In addition, I do not know if it is correct to introduce exporter, importer and time effects in the model Thank you in advance, Estrella Gómez * * 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: Dependent variable in a tobit model***From:*Austin Nichols <austinnichols@gmail.com>

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